Item Scheduling System And Apparatus Therefor

Abstract

A film scheduling or booking system is provided in which pre-punched zip sets are employed for film selection and are compared with a master film card to determine whether the requested date is available. The requested date is then marked on the film card in an area arranged as a 365-day calendar. The marked areas on the master film card are optically scanned and both the master film card and the zip set are punched in the marked areas, all in the same operation. The master film card is provided with a reference area ahead of the calendar area and the output of the twelve channels of the optical scanning circuits are all automatically set to a fixed reference level so that thermal drift or saturation of the sensing devices in either the plus or minus direction does not produce improper punching.

Description

The present invention relates to an item scheduling or booking system, and more particularly, to a scheduling system whereby any desired items may be distributed from a central location on a rental or loan basis to a number of widely separated consumer locations. While the present invention is particularly designed for and will be described in connection with a film library wherein films may be stored at a main distribution point and distributed to various schools in a given school district, or county, it will be understood that the arrangement of the present invention is equally well suited for use in the scheduling of any other rental or loan items, such as film projectors, room reservations, car rental or other rental items, etc.

While various systems have been heretofore proposed for the scheduling and distribution of various items, these systems have in general been unsatisfactory due to the fact that they require costly and complicated apparatus; the items cannot be readily selected by relatively unskilled persons at the various locations in which the items are to be used; and the scheduling system is not entirely foolproof from the standpoint of insuring that the items requested are available on the dates requested.

It is an object, therefore, of the present invention to provide a new and improved item scheduling arrangement which avoids one or more of the discussed disadvantages of prior art arrangements.

It is another object of the present invention to provide a new and improved item scheduling apparatus in which dates on which a particular item is available may be marked photosensitive field effect transistor, indicated generally at 262 and commonly called a photofet, is positioned in the upper end of each aperture 258, each of the photofets 262 being positioned within a sealed housing 264 in the end of which is positioned a transparent window 266. relatively close to the assembly 254 and to the bed 252 so as to on a master card pertaining to the item in question, and the marked areas are optically sensed and then punched both in the master card and in a duplicate set of soft and hard copies, all in the same operation.

It is still another object of the present invention to provide a new and improved optical scanning arrangement for optically sensing marked areas on an IBM card.

It is a further object of the present invention to provide a new and improved apparatus for optically sensing marked areas in an IBM card and simultaneously punching the marked areas in the same card in a single operation.

It is a still further object of the present invention to provide a new and improved optical sensing arrangement for sensing marked areas in an IBM card wherein the output level of the sensing device is automatically standardized to a fixed reference level before optical sensing is started.

It is another object of the present invention to provide a new and improved optical scanning arrangement for detecting blank marks on an IBM card wherein saturation of the optical sensing equipment is prevented from causing improper punching of the card.

Briefly, the present invention embodies an arrangement wherein multiple copy form sets, or so-called zip sets, are employed for selection of a particular item requested from a main distribution point at particular dates. The zip set is compared with a master card file and if the requested dates are available, the master card is marked by means of a black marker in the areas corresponding to the requested dates. The marked master card is then optically sensed, and both the master card and the zip set are punched in the marked areas, all in the same operation.

The optical scanning arrangement of the present invention is arranged to be added to a conventional IBM punch so as to provide the above-described sensing and punching operation. with a minimum of additional equipment.

During the optical scanning operation, a predetermined area of the master card is provided with individual reference areas which give a predetermined reflected light output and are optically sensed prior to scanning the marked areas on the card. The output of the optical sensing circuit is automatically set to a fixed reference level so that the effects of thermal drift or saturation of the sensing devices in either direction does not produce improper punching.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings in which:

FIG. 1 is a flow chart, in block diagram form, of the item scheduling system and apparatus of the present invention;

FIG. 2 is a block diagram indicating the basic electrical components employed in the apparatus of the system of FIG. 1;

FIG. 3 is a perspective view of a preferred arrangement employed for combined optical scanning and punching employed in the apparatus of FIG. 1;

FIG. 4 is a sectional view taken along the lines 4--4 of FIG. 3;

FIG. 5 is a sectional view shown on a somewhat enlarged scale, of one of the light sensing channels employed in the apparatus of FIG. 3;

FIGS. 6, 7 and 8 are diagrammatic views illustrating the operation of the apparatus of FIG. 3 in detecting darkened areas on an IBM card;

FIG. 9 is a schematic diagram showing the circuit arrangement of the optical scanning and output circuits shown in block diagram form in FIG. 2;

FIG. 10 is a graph illustrating the operation of the anti-saturation circuit embodied in the circuit arrangement of FIG. 9;

FIG. 11 is a timing diagram illustrating the correlation of various portions of the apparatus of FIG. 2 during the simultaneous punching operation;

FIG. 12 shows the correlation of the film card and zip set during the various punching operations in the system of FIG 1; and

FIG. 13 is a fragmentary view of a portion of the film card shown in FIG. 12 showing the auto-zero reference marks employed therein.

Referring now to the drawings, the present invention is therein illustrated in conjunction with a film scheduling or booking system whereby any one of a large number of films stored in a central film library may be requested by teachers in different schools served by the central film library on a loan or rental basis; the allocation of the desired films on specified dates may be handled in an efficient and entirely automatic manner whereby confirmation of the order is made; correlation of all requested dates is maintained in a master file; and appropriate shipping, tabulating and accounting data simultaneously provided in a minimum number of operations and on an economical basis.

More particularly, the present invention contemplates the use of a packet or set of blank office forms with carbons between sheets or sheets of NCR paper, indicated generally at 11. This packet is commonly called a zip set and comprises a top blue copy, a pink copy and two hard IBM cards all of which are initially secured together as a set and are arranged to be individually torn apart. This zip set is preferably arranged as shown at 11 in FIG. 12 and comprises a first area indicated generally at 15 in which numerical information identifying a particular school can be punched, a second area 17 which is initially blank and is filled in by the teacher as will be described in more detail hereinafter, a third area indicated generally at 19 which comprises a 365-day calender which includes a first column 21 starting, for example, with the number 8 signifying August for the first school month of the year, following by 31 vertical columns for each day in the month, and a further vertical column 23 in which the corresponding months are spelled out. An area 25 is provided on the zip set 11 in which numerical information corresponding to the title number of the film requested, its copy number and size, may be punched. A further area 27 in the lower left-hand corner of the zip set 11 is provided for imprinting of the name and address of a particular school.

A file of master school cards, indicated at 12, is maintained at the film library, each of these cards comprising a plastic card of the same shape as the zip sets 11 and having holes punched therein in the area 15 corresponding to the particular number assigned to each school, as well as having an addressograph plate attached thereto in an areas corresponding to the area 27 of the zip set 11. Initially, each of the cards in the master school file 12 is placed in a Standard Register source record punch, which preferably comprises a model 1612 punch hereinafter identified as an SR punch, or SRP, which is modified to accomplish certain functions of the scheduling system of the present invention, as will be described in more detail hereinafter. A large number of blank zip sets 11 are run through the SR punch so that the area 15 thereof has punched therein numerical information corresponding to a particular school. This punching operation is indicated in the flow diagram of FIG. 7 as the block 14. During this same operation the addressograph plate on the master school card is employed to imprint the school name and address on each of the blank zip sets 11, this operation being indicated at 14a, this imprinting being made in the area 27 of the sets 11.

The group of blank zip sets which have thus been punched with the school number and imprinted with the school name are then supplied by the main film library to each school wherein they are maintained in the file 16. When a teacher at a particular school desires to make a request for a particular film, she looks up the desired film in a film catalog and fills out one of the prepunched zip set blanks from the file 16. More particularly, she fills out the film number on the line 29, the film title on the line 31, and the date requested on line 33. She then tears off the second or pink sheet of the prepunched blank and places it in her file 22, and then mails the remainder of the zip set to the film library, as indicated by the block 20.

At the film library, the booking or scheduling operator looks at the request received from the teacher and calls up the master film card corresponding to the film requested from a random access file 28, as indicated by the flow block 24. The master film card 13 is preferably of the form shown in FIG. 12 and comprises a first area 35 within which a number assigned to the particular film, together with its copy number and size, is punched. The number and title of the film are printed on the lines 37 and 39, respectively, to facilitate visual identification of the card. Next, a column 41 of reference indicia 119, one for each of the 12 months, is provided for automatic zeroing of the optical scanning equipment, as will be described in more detail hereinafter, following which an area indicated generally at 43 is provided which comprises a 365-day calender consisting of 31 columns each consisting of 12 vertically arranged boxes 45 (FIG. 13). The master film card 13 will contain punches in each of the boxes 45 which correspond to dates which have already been requested by other teachers. The scheduling operator compares the date requested with the dates which are not punched on the master film card 13 and ascertains whether or not the requested date is available, as indicated by the flow block 26.

If the requested date is not available, but other alternate dates are available, the scheduling operator sets an alternate date switch, as indicated by the flow block 30. The scheduling operator then takes a black marker, such as a felt tip marking pen or the like, and fills in the blocks 45 corresponding to the new date or dates on which the film will be reserved for the requesting teacher. For example, if the film is to be assigned to the requesting teacher on Aug. 3, the first block 45 in the third vertical column will be blackened by the scheduling operator, as indicated at 45a in FIG. 13, this operation being indicated by the flow block 32. The zip set 11 which has been received from the requesting teacher is then inserted into the SR punch, as indicated by the block 34. Also, the master film card is inserted into an IBM card punch, preferably of the type 029 Model A22, hereinafter referred to as the IBM punch, which is modified to incorporate optical scanning apparatus and associated program control circuits, as operation being indicated by the block 36. The program control apparatus employed to control both the SR punch and the IBM punch is then initiated so that optical scanning of the master film card 13 which has been marked with the newly requested dates as described above, is accomplished. Information relative to the marked blocks 45 is stored in a shift register and when the master film card 13 reaches the position of the punches in the IBM card punch, both the master card 13 and the zip set 11 are simultaneously punched at the dates which have been marked by means of control apparatus to be described in more detail hereinafter. The master film card 13 then moves to the pin sensing equipment of the IBM punch and the film number which is punched into the master film card 13 in the area 35 is then punched into the area 25 of the zip set 11 by the SR punch. These operations are indicated by the flow blocks 38 and 40.

The operator then separates the remaining sheets of the zip set 11 as indicated at 42, and sends the blue copy back to the requesting teacher who compares her pink copy in the file 22 with the received confirmation copy, as indicated by the block 46. If no dates are available for the requested film, the scheduling operator simply tears off the blue sheet of the zip set when the dates are compared with the master film card at 26, and mails the blue sheet back to the requesting teacher who compares this copy with her retained pink copy thus indicating a refusal to supply the film on the requested dates or any alternate dates, as indicated by the block 48.

The remaining hard copies of the zip set 11 are then retained at the film library and are supplied to appropriate shipping, tabulating and accounting facilities, as indicated by the block 44, so that the requested film may be forwarded to the requesting teacher on the date requested. One of these hard copies may be forwarded with the film and the return date indicated on this copy so that the teacher is informed of the date when the film should be returned. Another copy may be retained as a booking copy which can be compared with the shipping copy when the film is returned so as to facilitate tabulation and handling of the films in an automatic manner. The retained copy may also be employed for tabulation and accounting purposes.

Referring now to FIG. 2, the equipment employed to carry out the above-described series of operations is therein illustrated as comprising a main program control, indicated generally at 52, to which is supplied the standard keyboard output 54 of the IBM punch, a program drum output No. 1, indicated at 56, a program drum output No. 2, indicated at 58, a program selector, start and alternate date switches indicated at 60, and the pin sensing output 62 of the conventional IBM card punch. The optical scanning and auto-zero circuits are indicated generally by the block 64 and comprises a series of twelve optical scanning heads and appropriate circuitry for generating standardized pulses corresponding to the marked areas of the master film card, the outputs of these scanning heads being stored in a group of twelve shift registers indicated generally at 66.

The shift registers 66 function to store the information developed by the scanning heads for a period equal to the distance between the mechanical position of the optical scanning heads 64 and the position of the punches in the IBM card punch. To this end, the shift registers 66 are controlled by means of pulses derived from the IBM card advance escapement 74 which is supplied by way of the conductor 73 and through a pulse shaping network 68 as clock pulses to the shift registers 66. In a preferred embodiment, the shift registers 66 function to delay developing an output on the output conductors 69 thereof for a time period equal to 24 columns of the IBM card, corresponding to the distance between the optical heads and the IBM punch control circuits 70. The outputs of the shift registers 66 are supplied to optical scan output circuits 67 which are arranged to receive an enabling pulse from the central program control 52 over the conductor 71. During this enabling pulse, the output circuits 67 function to supply punch central pulses by way of the conductor 79 and through the control program control 52 to the IBM punch control circuits 70. Also, the circuits 67 function to supply delayed control pulses to the SRP punch control circuits 75 which are also provided with enabling pulses supplied over the conductor from the SRP control circuits 72. The SRP control circuits 72 also supply control pulses over the conductor 78 to the "alpha" lead of the IBM card punch which controls the card advance escapement of this punch. Accordingly, during the common punching operation, the IBM punches 70 are actuated at the same time as the SRP punches 75 but under the control of the SR control circuits 72.

Referring now to a preferred arrangement for the optical scanning circuits 64, reference may now be made to FIGS. 3 to 8, inclusive, wherein such an arrangement is shown. In FIG. 3 the bed of the IBM card punch along which the master film card is advanced in the direction of the arrow 250 is indicated generally at 252 and the optical scanning assembly, indicated generally at 254, is mounted above the bed 252 and ahead of the conventional punches 256 of the IBM card punch by a distance equal to twenty-four columns. The conventional IBM pin sensing equipment 62 is positioned a distance somewhat more than the length of an IBM card to the left of the punches 256, as shown in FIG. 3.

A master film card 13 is advanced along the bed 252 by means of the card advance mechanism of the IBM card punch and the assembly 254 is arranged to detect optically the presence of darkened areas 45a in the regions of one or more of the boxes 45 on this card as this card is advanced in a step-by-step fashion past the assembly 254. To this end, a series of 12 elongated vertical apertures 258 are provided in the assembly 254, the bottom end of each aperture terminating in a narrow light entrance 260. A photosensitive field effect transistor, indicated generally at 262 and commonly called a photofet, is positioned in the upper end of each aperture 258, each of the photofets 262 being positioned within a sealed housing 264 in the end of which is positioned a transparent window 266. Preferably, the interior of each of the openings 258 between the window 266 and the entrance 260 is threaded and painted black to reduce light reflections in transmission to the photofet 262. A pair of elongated, tubular, frosted light bulbs 80 and 82 are employed as a common light source for all of the 12 photofets 262, the light bulbs 80 and 82 being positioned relatively close to the assembly 254 and to the bed 252 so as to provide constant, shadowless illumination under conditions of reflection from the master film card 13 except in the blackened areas thereof.

In order that the scanning assembly 254 will not respond to already punched areas of the master film card 13, the bed 252 is provided with a series of openings 270 therein each of the openings 270 being positioned immediately below one of the openings 260 in the assembly 254. A light source 272 is positioned beneath the bed 252 and is arranged to direct light upwardly through the openings 270. Preferably, the light source 272 comprises individual miniature of so-called grain of wheat light bulbs, one for each of the openings 270, which are of smaller diameter than the openings 270 and are positioned one in each of these openings in the bed 252 which is of sufficient thickness to accommodate these bulbs without projecting above the upper surface of the bed. With such an arrangement all of the light from each bulb is directed upwardly and hence the bulbs may be 12 V. bulbs operated at 6 V. DC for long life characteristics.

Considering now the manner in which the darkened portions 45a on the master film card 13 are detected by the assembly 254, as the card 13 is advanced under the assembly 254, light from the light bulbs 80 and 82 is reflected off of the upper surface of the card 13, enters the openings 260 and strikes the photofet 262 in each of the twelve channels of the assembly 254, as shown in FIG. 6. If the card 13 has already been punched during a preceding scheduling operation, so that an opening 45b is present in one of the boxes 45 of the card 13, the reflectivity of light from the sources 80, 82 is interrupted but light from the light sources 272 is directed upwardly through the aligned openings 270 and 260 in the particular channel containing the opening 45b, and strikes the photofet 262 so that its electrical output does not change, but remains at full illumination value, as illustrated in FIG. 7. In this connection it will be understood that light from the sources 272 is, under all other conditions, blocked by the card 13 itself.

When a blackened area 45a on the card 13 passes beneath one of the openings 260 in the assembly 254, light from the sources 80, 82 is absorbed and is not reflected upwardly to the corresponding photofet 262 so that the light incident upon this photofet falls to a low value. This decrease in light supplied to the photofet 262 is then employed in the associated circuitry shown in FIG. 9 to develop an output pulse in circuitry which has previously been standardized in an automatic zeroing operation and is then supplied to the corresponding shift register 66, as will be described in more detail hereinafter in connection with FIG. 9.

The bottom edge 274 of the scanning assembly 254 is preferably spaced approximately one-eighth inch from the upper surface of the master film card 13 as this card is moved along the bed 252. If the assembly 254 is spaced more than this distance away from the reflective surface of the card 13, light will be reflected from the light areas surrounding one of the blackened areas 45a with the result that sufficient light will be directed to the photofet 262 to prevent the sensing of the desired blackened area 45a. On the other hand, if the assembly 254 is too close to the reflective surface of the card 13, shadows will be produced which will interfere with the desired maximum illumination of the photofet 262 under all conditions except the presence of a blackened area 45a. Furthermore, the optical scanning assembly 254 becomes more sensitive to card warpage and creasing with such close spacing of the assembly 254 and the card 13. In this connection it will noted that the optical scanning assembly 254 avoids the use of fiber optics and optical lens systems on which dust and dirt can collect and hence interfere with the accurate sensing of the blackened areas 45a. In the arrangement of the present invention, light is transmitted to the photofet 262 or blocked therefrom only through intervening air spaces and no optical surfaces are provided on which dust can collect and interfere with light transmission.

In accordance with a further important feature of the invention, the areas surrounding the boxes 45 are a shade of grey which is half way between black and the background color of the card 13 itself, which color appears within the boxes 45. If the areas surrounding the boxes 45 are black the IBM punches 256 will be actuated if the card 13 becomes slightly out of registration with the optical scanning assembly 254 during the optical scanning cycle. On the other hand, if the areas surrounding the boxes 45 are of the same color as the areas inside these boxes, then the sensitivity in detecting marked areas 45a is reduced unless the booking operator is careful to completely cover the box 45 with a black mark. This is because the area viewed by the photofet 262 is somewhat larger than the area of the box 45. However, when the area surrounding the boxes 45 is half way between black and the background color of the card, the booking operator need fill only about sixty percent of the box 45 with a black mark to insure that the black mark is detected. Also, the card 13 may be slightly out of registration without producing incorrect reading. This is because the area outside of the box 45, being half way between black and background color of the card is equivalent to the reference level set during auto-zero and hence neither reduces sensitivity nor causes incorrect triggering of the punches.

Referring now to FIG. 9 wherein the detailed circuitry of the optical scanning and AUTO-ZERO circuits 64, and the optical scan output circuits 67 are shown, the frosted lamps 80 and 82, are arranged to be energized by a regulated 90 V. DC source 84 which is energized from the conventional 110 volt AC supply. The bulbs 80, 82 are preferably 25 watt bulbs which provide suitable illumination for all of the channels of the optical scanning assembly 254. Light from the sources 80, 82 strikes the photosensitive gate element of the photofet 86 except in a particular channel in which a blackened area 45a is present. The gate element of the photofet 86 is connected through the resistor 88 to the arm of a potentiometer 90 connected between -6 V. and -12 V. so that the bias on the gate of the photofet 86 may be varied by adjustment of the potentiometer 90. The drain element of the photofet 86 is normally connected through a load resistor 92 and a potentiometer 94 to the junction of a resistor 96 and a resistor 140. The resistor 96 is connected to +6 V. and the resistor 140 is connected to ground through the relay contacts 137, 138 under all conditions of operation except during the auto-zero step of the program cycle and the values of the resistors 96 and 140 are chosen so that a potential of +5 V. appears at the junction of these resistors. The source element of the photofet 86 is connected to the -6 V. supply.

Under normal conditions, light will strike the photosensitive gate element of the photofet 86 and a corresponding current will flow in the above-described drain circuit, this voltage being applied to the base of an emitter follower transistor 98, the collector of which is connected to +5 V. at the junction of the resistors 96 and 140 and the emitter of which is connected through a resistor 100 and a resistor 103 to -12 V. The signal developed across the emitter resistor 100 is directly connected to the base of a second emitter follower transistor 101, the emitter of which is connected through a resistor 104 to +12 V. and the collector of which is connected through a resistor 102 to the junction of the resistors 100 and 103. There is thus produced across the output resistor 104 of the transistor 101 a voltage which has a level corresponding to the illumination level on the gate element of the photofet 86.

The voltage developed across the resistor 104 is applied through an auto-zero storage capacitor 106 to the gate element of a field effect transistor 110, this gate element being also connected to the cathode of a diode 108 the anode of which is connected to -12 V. The drain element of the field effect transistor 110 is connected to +12 V. and the source element of this transistor is connected through the resistor 112 to ground. This source element is connected through a resistor 114 to the base of a transistor 116 the emitter of which is connected to ground and the collector of which is connected through a resistor 118 to -12 V. The collector of the transistor 116 is also connected through a Zener diode 120 and a resistor 122 to the -12 V. supply.

The output of the photofet 86 may vary from a value of plus five volts when the photofet is nonconductive, i.e., when no light is transmitted to its photosensitive gate element, to a value of approximately -6 V. when the photofet 86 is fully conductive, i.e., when full illumination strikes its gate element. Accordingly, the output voltage from the photofet 86 for light illuminations corresponding to black and card background are approximately centered about ground potential. In other words, ground potential represents an intermediate value of gray. However, the output of the photofet 86 may vary due to many factors including thermal drifts, voltage supply variations, changes in light reflection, maladjustment of the potentiometers 90 and 92, and other factors. Accordingly, if no provision were made for compensating for these factors the 24-bit shift register 132 in each optical scanning channel would be improperly triggered with the result that either a blackened area 45a would not be punched, or, in the other extreme, many punches would be made in the card where no blackened areas exist.

As discussed generally heretofore, and in accordance with an important feature of the present invention, an automatic correction or compensation circuit is provided so that regardless of drift in the photofet 86, and its subsequent amplifiers, the output of the transistor 116 is automatically set to a predetermined level when the master film card 13 is positioned for optical sensing of the automatic zero column 41. More particularly, when the optical scanning assembly 254 is positioned over the column 41 of the card 13, the openings 260 are positioned immediately above a series of reference blocks 119, one of these blocks being provided for each of the twelve optical scanning channels. Each of the blocks 119 comprises a central black area 121 on either side of which is positioned a background color area 123, the background color area 123 having the same combined areas as the black area 121. Accordingly, the area seen by each photofet when in the auto-zero column 41, is an area comprising one-half black and one-half background color which corresponds to a "gray" intermediate point generally corresponding to zero or ground potential at the output of each photofet 86. In the alternative, the areas within the reference blocks 119 may comprise a solid gray color having a shade half way between black and the background color of the card 13, i.e., the same shade of gray which surrounds the blocks 45, as described heretofore.

When the master film card 13 is stepped to the auto-zero column 41, a relay 128 is energized from the central program control 52 and the relay 128 controls a pair of switching circuits in each of the optical scanning channels. In the channel shown in FIG. 9, one of these switching circuits comprises the movable contact 126 which is employed for auto-zero correction and the other switching circuit 138 of this pair, which includes the contact 137, 139 is employed as an anti-saturation circuit, as will be described in more detail hereinafter. When the relay 128 is energized, the movable contact 126 is connected to the fixed contact 127 and over the conductor 130 to the right-hand side of the capacitor 106. The movable contact 126 is also connected by way of the conductor 124 to the junction of the Zener diode 120 and the resistor 122.

The auto-zero correction is employed to set the output of the transistor 116 at the correct level for triggering the shift register 132 irrespective of the photofet output at the time the correction is made. Since both the transistor 116 and the shift register 132 are energized from +12 V., the zero correction level is chosen to be +6 V., corresponding to a midpoint between the black and white extremes, and the drop across the Zener diode 120 is added in the opposite polarity so that the sum of these two voltages is approximately ground potential. The field effect transistor 110 develops a current gain in its output resistor 112 and the transistor 116 has a high voltage gain so that the output voltage appearing across the resistor 118 has a high amplification relative to the input applied to the gate element of the field effect transistor 110. When the Zener diode 120 is connected back to the input of the transistor 110 by closure of the contacts 126, 127, the transistors 110 and 116 act somewhat in the manner of an operational amplifier to insure that substantially zero volt is applied to the input of the amplifier when feedback is present, i.e., when the contacts 126, 127 are closed. However, since the Zener diode 120 has a voltage drop of approximately 6 V. and the total swing at the collector of the transistor 116 is approximately 12 V., the amplifier circuit including the transistors 110 and 116 will automatically adjust itself, due to the feedback connection through the contacts 126, 127, so that the potential at the collector of the transistor 118 is approximately +6 V. This plus six volt potential when added to the drop across the Zener diode 120 brings the potential at the gate element of the transistor 110 back to ground potential.

While the right-hand side of the capacitor 106 is thus connected effectively to ground potential during the auto-zero operation, the voltage across the resistor 104, i.e., the photofet output, may not be equal to ground potential depending upon the above-described factors, including thermal drift and the like. Accordingly, the capacitor 106 is quickly charged to absorb the voltage differential between the emitter potential of the transistor 101 and the gate of the transistor 116. Furthermore, when the auto-zero operation is terminated, i.e., when the master film card 13 is stepped to the first column of boxes 45 to be sensed, the relay 128 is de-energized but the capacitor 106 holds its charge for the remainder of the optical scanning cycle since it cannot discharge either through the diode 108 or through the field effect transistor 110 which has a very low current drain at its gate element. Accordingly, whenever the central program control circuits 52 call for an auto-zero correction, the output of the transistors 116 which are employed to control the shift registers 132 in each of the twelve channels are all automatically set to a predetermined reference value of approximately +6 V. and this reference voltage is maintained throughout the remainder of the optical scanning cycle.

The output voltage at the drain of the photofet 86 is initially adjusted to ground potential by moving the master card 13 to the automatic zero position 41 and holding while potentiometers 90 and 94 are adjusted in each of the optical scanning channels. Since the base-emitter contact potentials of the succeeding transistors 98 and 101 are of equal value and of opposite polarity the potential at the emitter of transistor 101 is likewise at ground. However, the outputs of the photofets 86 may become saturated in either the positive or the negative direction for any one of a number of reasons. If one of the light sources 80, 82 burns out, the output of the photofets may become saturated in the plus or black direction. Also, one of the potentiometers 92 or 90 may be mis-adjusted so as to produce an incorrect output in one of the photofets 86. Or, one of the photofets 86 may burn out, causing a plus saturation potential or may become shorted to cause a negative saturation potential. In order to avoid the effects of such saturation, which would cause multiple punching for saturation in one direction, or a total absence of punching in the opposite direction, the above-described auto-zero correction is correlated with a re-adjustment of the voltages applied to the photofet input circuit during auto-zero so as to positively prevent such type of operation. Thus, as shown in FIG. 10, and as discussed heretofore, the output of the photofet 86 is normally limited in the plus direction to plus five volts by the voltage developed across the voltage divider network 96, 140. On the other hand, the photofet output is normally limited in the negative direction by the -6 V. potential applied to the source element of this transistor. However, during the auto-zero correction when the relay 128 is energized, the movable contact 138 is connected to the fixed contact 139. When this occurs, the plus voltage limit of the photofet 86 is raised to a value of +6 V. as indicated by the dotted line 141 in FIG. 10. At the same time, when the contacts 138, 139 are closed, the right-hand side of the resistor 142 is connected to ground so that the voltage at the junction of the resistors 100 and 102 is increased from -6 V. to a value of -5 V., i.e., the dotted line 143 in FIG. 10.

Considering first the situation in which the photofet output is saturated in the positive direction, during the auto-zero correction the plus level is raised to the value 141, i.e., +6 V. so that the capacitor 106 is charged positively by a proportionate amount. However, after the auto-zero correction, the maximum plus saturation level goes back to +5 V. and since the charge on the capacitor 106 cannot leak off, the voltage at the gate element of the transistor 110 is minus one volt and is maintained at this value. Accordingly, the maximum saturated output of the photofet during the remainder of the optical scanning cycle will remain below the triggering level, thereby assuring that no multiple punching will be produced even though the output of the photofet remains saturated at a value eqaulling the maximum black level. On the other hand, if the output of the photofet becomes saturated in the negative direction to a level of -6 V., during the auto-zero correction the minus level 143 is raised to a value of -5 V. and the capacitor 106 is charged in the opposite direction to this voltage level. After auto-zero correction the minus saturation level goes back to -6 V. so that the gate element of the transistor 110 becomes -1 V., i.e., is operated below the triggering level and multiple punching is avoided. However, if the photofet responds to a black area 45a by changing its output in the plus direction an amount more than 1 volt the triggering level will be exceeded and a signal will be stored in the shift register 132 so that black areas are not missed. In this connection it will be understood that the output of the photofet 86 is normally at the -6 V. level unless a black area 45a is encountered. When this occurs, the photofet may be rendered completely nonconductive, as indicated by he positive voltage increase 145. When the master card 13 is moved to the next column so that the area 45a is no longer under the assembly 254, the voltage decreases back to -6 V., as indicated at 147 in FIG. 10.

Considering now the optical scan output circuits 6 which are also shown in detail in FIG. 9, the output of the shift register 132 is supplied by way of the conductor 136 and through a resistor 144 to the base of a transistor 146 the emitter of which is connected through a diode 150 to +6 V. and the collector of which is connected through a resistor 152 to ground. The base of the transistor 146 is also biased positively through the resistor 148. The transistor 146 acts as a limiter and provides decoupling from the shift register output. The output appearing at the collector of the transistor 146 is directly connected to the base of a transistor 154 the collector of which is connected to +6 V. and the emitter of which is connected through a resistor 156 to the base of a transistor 158. The emitter of the transistor 158 is connected to ground and the collector of this transistor is connected through the resistor 160 and the resistor 162 to plus 48 volts. The transistor 154 provides current amplification and the transistor 158 provides voltage amplification. The voltage appearing at the junction of the resistors 160, 162 is supplied to the base of a transistor 164 the collector of which is connected through a diode 166 to ground and the emitter of which is connected through a diode 168 to a terminal 172 which is arranged to be energized from the central program control 52 over the conductor 71 by means of +48 V. pulses which correspond to the IBM pin sense enabling pulses, these pulses lasting only for a duration equal to the time when the IBM punch circuits 70 are enabled in the IBM card punch. Accordingly, during this interval the transistor 164 is supplied with plus 48 volts on the terminal 172. Since this enabling pulse is applied to the terminal 172 at each column position of the IBM card punch, when a positive signal appears on the output conductor 136 of the shift register 132, 24 columns after it has been sensed by the optical scanning assembly 254, the transistor 164 is enabled so as to send an output pulse to both the IBM punch control circuits 70, and the SRP punch control circuits 75. More particularly, the signal developed at the emitter of the transistor 164 which lasts only for the duration of the pulse applied to the terminal 172, is supplied by way of a conductor 202 to the movable contact 208 of a relay 206. When the pulses developed by the optical scanning assembly 254 are to be supplied to the IBM punch control circuits 70 the relay 206 is de-energized so that the contact 208 is connected to the fixed contact 210 and these control pulses are supplied to the circuits 70 to actuate the IBM punches 256. Since the enabling pulses appearing at the terminal 172 are supplied to all 12 channels of the optical scanning system, the diodes 168 are provided in each channel for decoupling and to prevent signals generated in one channel from being transferred to another channel when one or more of the transistors 164 are rendered conductive.

The signal developed at the emitter of the transistor 164 is also employed simultaneously to control the SRP punch control circuits 75. However, the SRP punches are enabled a considerable time interval after the corresponding IBM punch has completed its stroke. Accordingly, it is necessary to delay the signal developed at the emitter of the transistor 164 in order to simultaneously actuate the SRP punch control circuit 75. In order to understand more clearly the relative timing of these pulses, reference may be had to FIG. 11 wherein a timing diagram of the respective pulses is shown. Referring to this figure, the +48 V. pulse which is supplied to the "alpha" lead of the IBM card punch to control the card advance escapement of this punch, is shown in FIG. 11 as the pulse 300. The pulse 300 is developed by the SRP after the start switch 60 has been depressed and the program drum 56 has caused the IBM punch to skip to column 13 of the master card 13 and at that point to call for the duplicate mode of operation for the IBM punch. At that time the SRP is energized and the SRP duplicate relay is pulled in for the remainder of the cycle. The electrical portion of the SRP is fully enabled a short time after the first pulse 300. The enabling pulse applied to the terminal 172 from the IBM pin sense enabling circuit is illustrated in FIG. 11 as the pulse 302 and during the interval of the pulse 302 the transistor 164 is enabled and sends a pulse over the conductor 202 to the IBM punch control circuits 70 so as to actuate the corresponding one of the IBM punches 256.

The pulse developed at the emitter of the transistor 164 is coupled through a charging diode 174 and a resistor 176 to a time delay network including a capacitor 180 and a shunt resistor 178, this network being connected between the base of a transistor 182 and ground. The collector of the transistor 182 is connected to -48 V. and the emitter of this transistor is connected through a resistor 184 to ground. The voltage developed at the emitter of the transistor 182 is coupled through a resistor 186 and a Zener diode 188 to the control electrode of a silicon controlled rectifier 190 the cathode of which is connected to ground and the anode of which is connected through a large resistor 192 to plus 75 volts. The anode of the silicon controlled rectifier 190 is also connected through a diode 194 to the punch solenoid 196 of the SRP punch control circuits 75 which corresponds to the optical scanning channel which is being scanned by the photofet 86. The solenoid 196 is connected through a cam switch 198 of the SRP punch control circuit 75 to a -75 V. supply. The other solenoids corresponding to the other 11 channels are likewise connected to the cam switch 198 as indicated by the multiple connections 197.

Considering now the manner in which a suitably shaped pulse is formed so as to actuate the SRP punch control circuit 75 in synchronism with the IBM punch, so that both the master film card 13 and the zip set 11 are punched simultaneously with the desired reservation dates, it is first pointed out that the enabling pulse which is supplied from the SRP control circuits 72 to the SRP punch control circuit 75 over the conductor 77 is in the form of a 50 millisecond pulse 304 (FIG. 11) which is delayed approximately 35 milliseconds after the IBM pin sense enabling pulse is applied to the terminal 172, i.e., after the IBM punch control circuits 70 have been actuated. In order to provide a control signal during the period of the SRP enabling pulse 304, a time delay or pulse stretching function is provided by the capacitor 180 and its associated circuitry so that the wave form applied to the base of the transistor 182 and coupled through the Zener diode 188 to the control electrode of the controlled rectifier 190 is as indicated by the wave form 306 in FIG. 11. It will be noted that the wave form 306 decreases gradually, as indicated by the portion 308, after the termination of the pulse 302 but the decreasing portion 308 has a magnitude substantially above the firing level of the rectifier 190, indicated by the dotted line 310, at the start of the SRP enabling pulse 304. As a result, the appropriate one of the solenoids 196 in the SRP punch control circuits 75 is energized, by conduction of the rectifier 190 during the shaded portion of the pulse 304 so that a corresponding punch is made in the zip set 11 at the same reservation date as the marked area 45a on the card 13.

As stated heretofore, the enabling cam switch 198 is common to all 12 channels of the optical scanning system and is closed for the duration of the pulse 304 (FIG. 11). However, none of the solenoids 196 should be energized, and hence none of the silicon controlled rectifiers 190 should be rendered conductive, unless a control pulse 306, 308 is present on the control electrode thereof. On the other hand, if the rate at which potential is applied to the anode of the rectifier 190 exceeds a predetermined value, the control rectifier 190 will fire even though no enabling pulse 306, 308 is present on its control electrode. In order to resolve these conflicting requirements, and in accordance with a further important feature of the invention, the resistor 192 has a large value of approximately 1 megohm, and is connected between the anode of the rectifier 190 and plus 75 volts. The resistor 192 is of such high value that the current through the rectifier 190 is limited to a value less than its holding current so that the rectifier 190 cannot fire unless a control pulse is present on its control electrode. However, the resistor 192 does not function to apply +75 V. to the anode of the rectifier 190 at all times. When the cam switch 198 is closed, a low impedance circuit consisting of the solenoid 196 and the diode 194 is now connected in parallel with the resistor 192 so that the rectifier 190 is then enabled to respond to a control pulse 306, 308. However, this connection of a low impedance circuit into the anode circuit of the rectifier 190 is not accompanied by a rapidly changing voltage increase on the anode of the rectifier 190 since this voltage is already at 75 V. due to the presence of the resistor 192. Accordingly, if the switch 198 is closed and no enabling pulse is present on the control electrode of the rectifier 190, the rectifier 190 does not fire when the low impedance circuit comprising the solenoid 196 and a diode 194 is connected in parallel with the resistor 192. However, if the control pulse portion 308 is present on the control electrode of the rectifier 190, this rectifier fires and energizes the solenoid 196 so as to actuate the SRP punch. If, on the other hand, the resistor 192 were omitted, when the solenoid 196 and diode 194 were connected into the circuit each time the cam switch 198 closes, the resulting potential rise at the anode of the rectifier 190 would cause this rectifier to fire irrespective of the control pulse 308 so that all of the punches in the SRP control circuit 75 would respond by punching holes in the zip set 11 when no control pulses are produced in the corresponding optical scanning channels. The arrangement of the present invention thus insures against misfiring of the controlled rectifiers 190 in the individual optical scanning channels. The rectifiers 194 provided in each channel also provide decoupling as regards hash appearing on the common terminal to the cam switch 198 and avoids cross coupling between the solenoids 196. The Zener diode 188 affects the triggering level 310 of the rectifier 190 and insures that the decaying portion 308 of the control wave form does not remain above the triggering level 310 long enough to cause the corresponding SR punch to be actuated twice in response to one control signal.

As discussed generally heretofore, the central program control 52 is arranged to control the SRP punch control circuits 75 from the IBM pin sensing equipment 62 after the optical scanning cycle has been completed so that the film number which has already been punched in the area 35 of the master film card 13 is punched in the area 25 of the zip set 11 so that the film number will be available in punched form in all of the zip set copies for use in automatic tabulation, shipping and accounting functions in connection with the shipment, storage, etc., of the corresponding film. More particularly, when a master film card 13 is manually inserted into the IBM card punch, is moved to the start position, and the start switch 60 is depressed, the central program control 52 under the control of drum 56 functions to move the master film card 13 immediately to column 13 before movement of the zip set 11 is commenced in the SRP, so that as far as the respective card advancements are concerned, the card 13 is offset with respect to the zip set 11 in the manner shown in FIG. 12. In this connection it will be understood that the master film card 13 is optically sensed and punched in the IBM card punch whereas the zip set 11 is punched in the SRP so that the card 13 and zip set 11 are not actually in the side-by-side relation shown in FIG. 12.

When the master film card 13 has been moved to column 13, so that the offset relation shown in FIG. 12 is achieved, the IBM card punch is programmed to the duplicate mode, the SRP control circuits 72 are enabled, over the conductor 76, and a pulse 300 is applied over the conductor 78 to the alpha input of the IBM card advance, so that the IBM card punch is made to travel in synchronism with the SR punch. This control of the IBM punch advance from the SRP is necessary because the normal rate of advance of the SRP is considerably slower than the IBM punch and yet and two are to be simultaneously controlled in accordance with data received during the optical scanning cycle.

The master film card 13 and the zip set 11 then move in synchronism to the left, as viewed in FIG. 12. When the automatic zero column 41 in the card 13 is reached, each of the twelve optical scanning channels is automatically set to the desired reference value, as discussed in detail heretofore. Thereafter, the blackened areas 45a in the calender area 43 are detected by the optical scanning system, and 24 columns later the same blackened area of the card 13 is presented to the IBM punches 256 so that the blackened area is punched in the card 13. After the above-described time delay interval between the pulses 302 and 304 (FIG. 11) and during the period when the zip set 11 is held stationary at the same column in the SRP, the SRP control circuits 72 are actuated so that the corresponding area of the calender 19 of the zip set 11 is also punched.

The card 13 and zip set 11 continue to be moved in synchronism until the end of the calender area 43 is reached. At this time, the master film card 13 is released by the IBM card punch and is moved automatically to the pin sensing equipment 62 of the IBM card punch in a conventional manner while at the same time the program drums 56 and 58 are reset to zero. As these drums are reset to zero the normally produced PCC-1 signal of the IBM card punch, which is developed as this machine moves from column 80 to column 88, is employed by the central program control 52 to restart the IBM card punch with drum 58 controlling the next cycle. During this cycle the IBM card punch is placed in the duplicate mode, the SRP is energized in the manner described heretofore, and the pin sensing equipment 62 is energized to sense information in the first 13 columns which were skipped at the start of the previous cycle. The SRP then generates pulses on the conductor 78 so that the card 13 and zip set 11 again move in synchronism to the left as viewed in FIG. 12. However, the central program control 52 energizes the relay 206 so that the movable contact 208 is now connected to the contact 212. Accordingly, and in accordance with a further important feature of the invention, the output of the pin sensing equipment 62 is now connected through the optical scan output circuit 67 so as to control the SRP punch control circuits 75 to punch the film number sensed in the first 13 columns of the master card 13 in the area 25 of the zip set 11. More particularly, when the contacts 208, 212 are closed, the film number in the master card 13 is sensed by the corresponding ones of the 12 sensing pins, and a control signal from the pin sensing circuits 62, which corresponds to the pulse 302, is supplied over the conductor 202, through the diode 174, the time delay network including the capacitor 180, and the transistor 182 to the control electrode of the rectifier 190. The rectifier 190 is thereby caused to fire so that the corresponding solenoids 196 in the SRP punch control circuit 75 are actuated with the result that the film number is punched in the area 25 of all the copies of the zip set 11. Since the master film card 13 has been moved past the IBM punches 256 before the pin sensing operation takes place, the IBM punch control circuits 70 may be actuated from the pin sensing equipment 62 through the conventional control equipment of the IBM card punch without any effect on the scheduling operation. However, if desired, the IBM punch control circuits 70 can be positively disabled during the pin sensing period in which the film number is punched in the area 25 of the zip set 11.

While but a single embodiment of the present invention has been here specifically disclosed, it will be apparent that many variations may be made therein, all within the true spirit and scope of the invention.

Claims

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a scheduling system, the combination of, a card marked in certain unpunched areas thereof with light absorbing material and having other previously punched areas, said unpunched areas and said punched areas both being arranged in a column extending transversely of said card, means for moving said card in steps along a predetermined path, optical sensing means individual to both said punched areas and said unpunched areas in a given column and positioned along a line transverse to said path, means controllable by said optical sensing means for developing individual output signals corresponding only to said marked unpunched areas in a given column, punching means positioned across said path and spaced from said optical sensing means by an amount equal to a predetermined number of steps along said path, shift register means for storing said output signals, means for pulsing said shift register each time said card is moved one step, and means connecting the output of said shift register to said punching means, whereby said marked unpunched areas in a given column are simultaneously punched in said card during a single pass along said path.

2. An arrangement as set forth in claim 1, wherein the areas surrounding said marked areas are of a shade approximately halfway between the marked areas and the background of said card.

3. The combination of claim 2, wherein said predetermined reference level is halfway between the maximum and minimum output levels of said optical sensing means.

4. A scheduling system, comprising a master card having a series of vertical columns representing days, each of said columns having vertically spaced areas representing months, certain ones of said areas in a given column being unpunched and containing marks of light absorbing material and certain other ones of said areas containing punches, a unit record card having unpunched areas corresponding to both said punched and unpunched areas of said master card, optical means for sensing said master card and producing output signals corresponding only to unpunched areas in a given column thereof containing light absorbing material, and means controlled by said output signals for substantially simultaneously punching said master card and said unit record card in areas corresponding only to said unpunched areas containing light absorbing material in a given column on said master card.

5. The combination of claim 4, wherein said master card has punches in another area thereof identifying a particular unit, second sensing means for sensing said last named punches, and means operative after said marked areas have been punched for punching said unit record card in areas corresponding to said last named punches in said master card.

6. The combination of claim 5, wherein separate punching means are employed for punching said master card and said unit record card, an amplifier for driving said unit record card punching means, and means for selectively applying the output of said first and second sensing means to the input of said amplifier.

7. In a scheduling system, a plurality of solenoids, a silicon controlled rectifier for each of said solenoids, means individually connecting one end of each of said solenoids to the anode of a different one of said rectifiers, means for applying an energizing potential to the other end of said solenoids in common, means for selectively applying control signals to the control electrodes of said rectifiers thereby to cause current flow of predetermined magnitude through the solenoid connected thereto when said control signal and said energizing potential occur simultaneously, and means independent of said solenoids for continuously supplying a potential to the anode of each of said rectifiers without exceeding the minimum holding current of each of said rectifiers.

8. The combination of claim 7, wherein said potential continuously supplied to the anodes of said rectifiers is of substantially the same magnitude as said energizing potential.

9. The combination of claim 7, wherein said means for continuously supplying a potential comprises resistances of high value individually connected to the anodes of said rectifiers.

10. A scheduling system, comprising a master card having a plurality of areas corresponding to different periods of time, certain of said areas being unpunched and marked by a layer of light absorbing material within the area and certain of said areas containing punches, said unpunched marked areas and said punched areas being interspersed in columns extending across said master card, a unit record card having areas corresponding to both said unpunched marked areas and said punched areas of said master card, optical sensing means individual to both said unpunched marked areas and said punched areas in a given column for sensing only said unpunched marked areas of said master card and developing control pulses in response thereto, first and second punching means, means controlled by said control pulses for actuating said first punching means to punch said master card in said unpunched marked areas, means for enabling said second punching means a predetermined time interval after said first punching means is actuated, means for delaying said control pulses, and means controlled by said delayed control pulses for actuating said second punching means during the interval of said enabling pulses, thereby to punch said unit record card in the same areas as said unpunched marked areas of said master card.

11. In a scheduling system, the combination of, a master card having a plurality of areas corresponding to different periods of time, said card being marked in certain unpunched areas with a light absorbing material within the area and having other ones of said areas punched, means for moving said card in steps along a predetermined path, light responsive means positioned above said path, a pair of light sources positioned above said path on either side of said light responsive means, means directing light emanating from said sources and reflected from unmarked areas of said card to said light sensitive means, means controlled by the output of said light sensitive means for punching said card in said marked areas thereof, and means for preventing the operation of said punching means in said prepunched areas of said master card.

12. The combination of claim 11, wherein there is provided an additional light source positioned beneath said path and arranged to direct light therefrom upwardly through punched areas of said card to said light sensitive means.

13. The combination of claim 11 wherein said light sensitive means includes a light sensitive field effect transistor.

14. The combination of claim 11, wherein the areas of said card which surround said time period areas are of a shade approximately halfway between the shade of said marked areas and the background shade of said card.

15. In a scheduling system, the combination of, a master card having a plurality of areas corresponding to different periods of time, said card being marked in certain of said areas with a light absorbing material, means for moving said card in steps along a predetermined path, light sensitive means positioned above said card and responsive to different areas thereof as said card is moved along said path, means controlled by said light sensitive means for developing an output signal in response to positioning of one of said marked areas beneath said light sensitive means, a reference area on said card and having a predetermined shade which is different from said marked areas of said card, and means operative when said reference area is positioned beneath said light sensitive means for adjusting said output signal to a predetermined reference level and independently of the output of said light sensitive means.

16. The combination of claim 15, wherein said reference area is ahead of said marked areas on said card and said reference level of said output signal is maintained as the marked areas of said card are moved beneath said light sensitive means.

17. In a scheduling system, the combination of, a master card having a plurality of areas corresponding to different periods of time, said card being marked in certain unpunched areas with a light absorbing material within the area, means for moving said card in steps along a predetermined path, light responsive means positioned above said path, a pair of light sources positioned above said path on either side of said light responsive means, means directing light emanating from said sources and reflected from unmarked areas of said card to said light sensitive means, an additional light source positioned beneath said path and arranged to direct light therefrom upwardly through punched areas of said card to said light sensitive means, and means controlled by the output of said light sensitive means for punching said card in said marked areas thereof.

18. In a scheduling system, the combination of, a card marked in certain unpunched areas thereof with light absorbing material and having other previously punched areas, said unpunched areas and said punched areas both being arranged in a column extending transversely of said card, said card having a reference area ahead of said column, means for moving said card in steps along a predetermined path, optical sensing means individual to both said punched areas and said unpunched areas in a given column and positioned along a line transverse to said path, means controlled by said optical sensing means for developing individual output signals corresponding only to said marked unpunched areas in a given column, punching means positioned across said path and spaced from said optical sensing means by an amount equal to a predetermined number of steps along said path, shift register means for storing said output signals, means for pulsing said shift register each time said card is moved one step, means connecting the output of said shift register to said punching means, whereby said marked unpunched areas in a given column are simultaneously punched in said card during a single pass along said path, and means operative when said optical sensing means is positioned over said reference area for automatically setting the output of said optical sensing means to a predetermined reference level.

19. In a scheduling system, a plurality of solenoids, a silicon controlled rectifier for each of said solenoids, means individually connecting one end of each of said solenoids to the anode of a different one of said rectifiers, means for applying an energizing potential to the other end of said solenoids in common, means for selectively applying control signals to the control electrodes of said rectifiers thereby to cause current flow of predetermined magnitude through the solenoid connected thereto when said control signal and said energizing potential occur simultaneously, means independent of said solenoids for continuously supplying a potential to the anode of each of said rectifiers without exceeding the minimum holding current of each of said rectifiers, and a diode connected between each of said solenoids and the anode of the corresponding rectifier to prevent cross coupling between said solenoids.

20. In a scheduling system, the combination of, a master card having a plurality of areas corresponding to different periods of time, said card being marked in certain of said areas with a light absorbing material, means for moving said card in steps along a predetermined path, a light sensitive field effect transistor positioned above said card and responsive to different areas thereof as said card is moved along said path, means controlled by said light sensitive transistor for developing an output signal in response to positioning of one of said marked areas therebeneath, a reference area on said card ahead of said marked areas and having a predetermined shade, means operative when said reference area is positioned beneath said light sensitive transistor for adjusting said output signal to a predetermined reference level and independently of the output of said light sensitive transistor, means for maintaining said reference level of said output signal as the marked areas of said card are moved beneath said transistor, means for supplying an energizing voltage to said transistor, and means for adjusting said energizing voltage during scanning of said reference area so that saturation of said transistor in the direction corresponding to a marked area of said card does not produce an output signal in unmarked areas of said card.