US3893097A - Dispatching system circuit - Google Patents

Abstract

A circuit for use in a dispatching system operable to efficiently direct the movement of dispatched units to two sets of serving stations, the system having actuating means at each set of serving stations for producing electrical request signals and having two electrically actuated instructing means, preferably direction-indicating signs, for directing movement to an associated set of serving stations. The circuit effects actuation of each instructing means in response to a request signal produced by actuating means at its associated set of serving stations, and effects alternate actuation of both instructing means in response to simultaneous storage of request signals produced by actuating means at both sets of serving stations.

Description

Lach et al.

DISPATCHING SYSTEM CIRCUIT Inventors: Ronald Louis Lach, Arlington Heights; William Jean Brier, Skokie, both of ill.

July 1, 1975 [73] Assignee: Elec-Tro-Tec, lnc., Elk Grove [57] ABSTRACT Village. ii]. A circuit for use in a dispatching system operable to efficiently direct the movement of dispatched units to [22] Flled' June 1974 two sets of serving stations, the system having actuat- [21 Appl. No.: 475,582 ing means at each set of serving stations for producing electrical request signals and having two electrically actuated instructing means, preferably direction- 2? 6 %33 indicating signs, for directing movement to an associ- I d 40/5? 286 ated set of serving stations. The circuit effects actua- 1 o are tion of each instructing means in response to a request signal produced by actuating means at its associated [56] References cued set of serving stations, and effects alternate actuation UNITED STATES PATENTS of both instructing means in response to simultaneous 2,482,610 9/1949 Burn 340/5] storage of request signals produced by actuating 0.0l0 l 1/1963 Smith .l 340/5! means at both sets of serving stations. 1158.836 ll/l964 McCauley 340/5l 10 Claims, 7 Drawing Figures LEFT RIGHT SERVING -11 SER V/NC STA 1100s 5m TIONS r2! ee REQUEST Rmuzs r smwnLs 5I6NALS .L' I I I LEFT RIGHT I I REGISTER RIGISTER .I I '16 I I I 32 I l I I I cawmat SWITCH l I I I (TIMER 0R TREADLE- I I l I :553? f OPERATED SWITCH) giaa i I I I l I Isramce sroRAaz I I I I |J I/SEGUENCER I/ 23 INITIA TING I I CONTROL [I I I I t 26 l I I I scauz/vcm 29 I RL'QUEST SIGMAJ (Rem/cs r SIG/VAL l I CANCELLATION I I CANCELLATION I I S fV f'SOLI "gs/ 5550c P84 27"! I LEFT INDICATOR lug/ 3 1 212 '#TF@-"T MuL-| 975 @53931397 SHEET 1 L EFT mam s: R vnvc 55 V/NG STA T/cws STA T/ONS f2! *&2

RE QUES r REG 05.5 r SIGNALS SIGNALS LEFT r45 [9v RIGHT REG/S TER REGISTER I I f I 32 *1 I co/vmoL sw/rcu (TIMER 0R TREADL E- I I REQUEST OPERATED SWITCH) REQuEs T I I sic/VA L I SIGMA L l I STORAGE N STORAG I I I :ISEGUENCER l 2 3 uw TIA TING I I CON TROL f I 26 I I- --I i I SEQUENC ER f a; REQUEST VGA/As) IREQUES T SIGMA L CANCELLATION i I CANCELLATION l a l l POWER POWER CONTROL: :c0/v 7R0!- P24 27% LEF T J I RIGHT IND/CA TOR INDICATOR SHEET ATFHTFnJuu F GE mmw KNEE. Qk

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N23 mu bout DISPATCHING SYSTEM CIRCUIT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to clectrically operated dispatching systems and, more particularly. to a novel circuit for use therein.

2. Description of the Prior Art Electrically operated dispatching systems, particularly suitable for, but not limited to, use in drive-in banks and the like have been provided for efficiently controlling the movement of vehicular or pedestrian traffic or other moving units from a dispatching or entrance station to a plurality of remote serving or receiving stations by accepting electrical request signals or teller calls from the stations as they are generated, and subsequently presenting instruction messages, preferably by means of visible displays, at the dispatching station in a predetermined sequence. See, for example, U.S. Pat. No. 3,206,722, which issued on Sept. l4, 1965 to O. T. Gustus, et al; and U.S. Pat. No. 3,588,808, which issued on June 28, 1971 to R. T. Gustus.

The dispatching systems typified by the disclosures of these patents efficiently direct or dispatch moving units, vehicles or customers to a plurality of remote receiving or serving stations in response to either manual and automatic entry of request signals from the stations into a centrally located dispatching system circuit by means of electric cables or wires installed from each station to circuit. However, in order to minimize the cost and inconvenience associated with such wired connections from each station to the central control circuit. it has been found to be economical and desirable to substitute radio control equipment for these wired connections, a radio transmitter being installed at each of the stations, and receiving equipment being provided at the centrally located control circuit. In order to minimize the cost of such radio control equipment. the receiving stations can be divided into two sets or groups, preferably corresponding to directions measured from the dispatching or entrance station, all of the stations in each set having identical transmitters operable to transmit request signals at a given frequency, thereby requiring the receiving equipment to receive signals at only two transmission frequencies. In such a system, the vehicles, pedestrians or other dispatched units can be arranged in a waiting line at the entrance station. Two instructing means, preferably comprising direction-indicating signs, can be provided to efficiently direct the movement of the dispatched units to the two sets of receiving stations.

Since prior known dispatching system devices are typically designed to accommodate a large number of receiving stations, they are not efficiently adaptable to a dispatching system for use with only two sets of re ceiving stations.

SUMMARY OF THE INVENTION The present invention comprises a circuit for use in a dispatching system operable to efficiently direct the movement of customers, vehicles or other dispatched units arranged in a waiting line to two sets or groups of serving or receiving stations, such as in banks, airline ticket terminals, store check-out counters and in other applications where it is important to minimize delays in receiving or serving the dispatched units. Such a system typically includes known actuating means at each of two sets of serving stations for producing electrical request signals and two electrically actuated instructing means, preferably direction-indicating signs. for directing movement of the waiting units to an associated set of serving stations. In general, the circuit of the present invention effects actuation of an instructing means in response to storage of a request signal produced by its associated set of serving stations, and effects alternate actuation of both instructing means in response to simultaneous storage of request signals produced by actuating means at both sets of serving stations. Novel register means are provided by the present invention for storing the request signals produced by each set of serving stations.

More specifically, the circuit of the present invention comprises: control switch means, sequencing means and two register means, each register means being associated with an instructing means, and being connected to the actuating means at an associated set of serving stations to store the request signals produced thereby, the sequencing means being in control circuit with each register means and the instructing means associated therewith and being operable to control actuation of the latter in response to storage of request signals in the register means, the sequencing means being operable to alternately control actuation of both instructing means in response to simultaneous storage of request signals in both register means, the sequencing means being further operable to cancel a request signal in each register means following each actuation of its associated instructing means, the control switch means being in control circuit with the sequencing means and each register means and being preconditioned upon storage of request signals to initiate operation of the sequencing means. The circuit of the present invention effects actuation of an instructing means in response to storage of a request signal produced by actuating means at its associated set of serving stations, and effects alternate actuation of both instructing means in response to simultaneous storage of request signals produced by actuating means at both sets of serving stations.

An important object of this invention is to provide an improved and reliable circuit for use in a dispatching system operable to direct the movement of units to each of two sets of serving stations.

Another important object of the present invention is to provide a circuit operable to store request signals from two sets of remote serving stations as they are generated, and to subsequently control the presentation of instruction messages at the dispatching station in a predetermined sequence.

Still another important object of the present invention is to provide a circuit for use in a dispatching system operable to effect alternate actuation of two instructing means in response to simultaneous storage of request signals produced by actuating means at two sets of serving stations.

Yet another important object of the present invention is to provide a dispatching system circuit which is simple in design, relatively inexpensive to manufacture, and efficient in operation.

Numerous other objects and advantages of the invention will be apparent from the following description, which, when taken in conjunction with the accompanying drawings, discloses a preferred embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a block diagram illustrating the basic fea tures and operation of the preferred embodiment of the circuit ofthe present invention. adapted for use in a directional dispatching system;

FIG. 2 is a schematic diagram illustrating the details of the left and right registers shown in FIG. I;

FIG. 3 is a schematic diagram illustrating the sequencer shown in FIG. 1;

FIG. 4 is a diagram illustrating a treadle-operated version of the control switch shown in FIG. I;

FIG. 5 is a schematic diagram illustrating an electronic timer version of the control switch shown in FIG. I; and

FIGS. 6 and 7 illustrate the control connections between the sequencer and visible and audible instructing devices.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, the present invention comprises a dispatching system circuit [0, enclosed within the dotted box in that figure, adapted for use in a directional dispatching system having known actuating means (not shown) at each of two sets or groups of serving or receiving stations, a set of left serving stations being diagrammatically indicated by reference numeral II, and a set of right serving stations being indicated by numeral 12. The acutating means can comprise either a manually operated or automatic switching device operable to produce request signals on calls. such as the devices disclosed in the previously men tioned U.S. patents.

The dispatching system further includes two known electrically actuated instructing means. each preferably comprising an electrically illuminated indicator sign with an audible chime (not shown), for an associated set of serving stations, a left indicator 13 being provided for directing attention or otherwise instructing the movement of dispatched vehicles, pedestrians, or other units toward the left set of serving stations illustrated at II, a right indicator 14 being similarly provided for the right set serving stations I2.

The circuit of the present invention comprises a control switch means I6, a sequencing means 17 and two register means I8 and I9, these devices also being illustrated within the dotted box in FIG. I. Each one of the registers I8 and I9 is associated with an instructing means or indicator; the left register 18 is associated with the left indicator 13'. and the right register 19 is associated with the right indicator 14. Each register I8, 19 is connected to the actuating means at an associated set of serving stations and is operable to store the request signals produced thereby, in a manner to be described. The left and right registers I8 and 19 are also connected to the left set of serving stations II and the right set of serving stations l2, by means of cable. wire or radio control connections 21 and 22, respectively.

The sequencer 17 is in control circuit relationship with the left register I8 and the left indicator l3 associated therewith, as represented by a dashed request signal storage line 23 and a power control line 24, respectively. Similarly, the sequencer I7 is in control circuit relationship with the right register I9 and with the right indicator 14, as represented by dashed lines 26 and 27, respectively. The sequencer I7 is operable, as will be described later. to control actuation of one indicator [3, I4 in response to storage of a request signal in the register I8. I9 associated with that indicator. The sequencer I7 is further operable to alternately control actuation of both of the indicators I3 and I4 in response to simultaneous storage of request signals in both registers 18 and 19. The sequencer 17 is also operable, as described later. to cancel a request signal in a register I8, 19 following each actuation of its associated instructing means or indicator l3, 14, the request signal cancellation being represented by dashed lines 28 and 29 to the left register 18 and the right register 19, respectively.

The control switch I6, which can comprise either an electronic timer or a switching means operated in response to the presence of a unit to be dispatched such as a treadIe-operated switch. is in control circuit relationship with the sequencer 17 as represented by a dashed line 31, and each of the registers l8 and I9, as represented by dashed lines 32 and 33, respectively, operation of the control switch being preconditioned upon storage of request signals from either of the registers to initiate operation of the sequencer.

As will be described in detail, the circuit I0 of the present invention effects actuation of an instructing means or indicator l3, 14 in response to storage of a request signal produced by actuating means at its associated set of serving stations II and 12, respectively. The circuit [0 effects alternate actuation of both of the indicators I3 and I4 in response to simultaneous storage of request signals produced by actuating means at both sets of serving stations I] and I2.

FIG. 2 is a schematic diagram illustrating the details of the left and right registers 18 and 19 of the circuit I0, some of the details of the right register stages being omitted both in the drawings and in the specification for simplification, since both registers are identical. In the drawings. standard detached relay contact notation is utilized, also for simplification. Each relay is designated by a two letter symbol preceding a slash and a numeral illustrating the number of operative contacts of that relay; each contact is designated by the two letter symbol and a number. For example. an AA/3 relay has relay contacts AAI, AAZ and AA3, all of these contacts being transferred upon energization of the AA/3 relay coil. The drawings show all relay contacts in their rest positions. corresponding to de-energized conditions of their respective relay coils.

The left register 18 comprises a shift register having three bistable multivibrator stages 34(a), 34(b) and 34(0), the register stages preferably comprising electromechanical relays, although solid state or other switching devices may be utilized. The register I8 may comprise as many multivibrator stages as is necessary to store request signals or calls; however, only three such stages are illustrated for simplification. The register stages (not shown) in the right register I9 are identical with the left register stages 34(0). 34(b) and 34(c), and will not be separately described.

Each of the bistable multivibrator stages 34(a), 34(b) and 34(c) has corresponding reference numerals and is identical in design and operation, with the exception that its relays may contain different numbers of contacts. Taking the multivibrator stage 34(0) as a typical example. as shown in FIG. 2 this stage comprises a steering relay or other suitable switching means 36ml designated AA/3, and a stabilizing relay 37(a) designated AB/4, both in circuit with a control input on a line 38(0), and a common terminal or line 39(0) through resistors 41(0) and 42(0) for relays 36(0) and 37(0), respectively. The AA/3 steering relay 36(0) is energized upon application of a predetermined voltage on the order of 40 volts DC to the terminal or line 39(0) through resistor 41(0) and a line 43(0) connected to ground through an AB] contact, the A814 stabilizing relay 37(0) being in its de-cnergized condition. Isolating diodes 44(0 46(0 47(0) and 48(0) are provided to prevent operation of the AB/4 relay for this condition. Energization of the AA/3 relay serves to switch the input line 38(0) to the ABM relay, by means of an AAl contact and the diode 48(0). to precondition energization of the AB/4 relay in response to a ground pulse on the input line. Upon energization of the AB/4 relay, an AB] contact transfers to provide a ground holding circuit to maintain the AB/4 relay coil energized through a line 49(0), the transfer of the ABI contact also serving to de-energize the AA/3 relay by interrupting its ground circuit. De-energization of the AA/3 steering relay 36(0) serves to precondition deenerization of the AB/4 stabilizing relay 37(0) in response to an additional ground pulse on the input line 38(0); an additional ground pulse grounds the AB/4 relay coil through the diode 46(0) and the AAl contact (this contact having transferred to its rest position upon de-energization of the AA/3 relay). Upon termination of the ground pulse, the AA/3 relay becomes energized as previously described. It is seen that the AB/4 stabilizing relay 37(0) is operable to provide a ground holding circuit to maintain one of the relays 36(0) and 37(0) in an energized condition and the other of the relays in a de-energized condition until energization of the latter. The relays 36(0) and 37(a) are therefore individually and alternately energized in response to sequential ground pulses on the input line 38(0). The energization of the steering relay 36(0) upon application of the predetermined voltage to the line 39(0) is the reset" condition of the bistable multivibrator stage 34(0); the energization of the stabilizing relay 37(0) is its set" condition. All stages will be reset merely by momentarily interrupting voltage to their commonly connected lines or terminals 39(0), 39(1)) and 39(0).

It should be noted that the voltages, component values and types illustrated in the drawings of the dispatching system circuit correspond to those typically found or utilized in such a circuit; however, it will be recognized that other voltages and components may be substituted for those illustrated, their selection being a matter of design choice. For example. the bistable multivibrator stages can comprise either relays or solid state switching devices.

Each register stage 18. I9 is connected to known actuating means at its associated set of serving stations, as noted earlier, the actuating means being operable to provide request signals or teller calls which comprise ground pulses. The left register 18 is connected to the left set of serving stations ll (FIG. 1) by means of lines 2i for providing on a left store line 51 (FIG. 2) a ground pulse representing a request signal. For use with a radio-controlled system. line 51 may be connected to the collector terminal of the last common emitter transistor stage of a receiver, a ground line 52 being connected to the receiver ground.

With a reference to FIG. 2, a ground pulse supplied to the left store line 51 causes a (L/3 relay designated by reference numeral 53 to become energized from a 40 volt D.C. source connected to a terminal 54 through a series-connected surge resistor 56 and a diode 57 when a capacitor 58, connected in parallel with the CL/3 relay, charges to the relay operating or pull-in voltage level for a purpose to be described. As noted earlier, the energization of each relay coil effects transfer of all of its associated relay contacts; accordingly, contacts CLI (FIG. 2), CLZ (FIG. 3) and CL3 (FIG. 3) transfer, the CL! contact closing to apply D.C. voltage from a terminal 59 to commonly connected lines 39(0), 39(b) and 39(c) of the left register stages 34(0), 34(1)) and 34(('), respectively, through a left register power line 61. This application of voltage to the left register stages causes the AA/3, BA/4 and CAM relay coils to become energized through resistor 41(0) and the AB] contact, a resistor 41(1)) and a BB] contact, and a resistor 4l(c) and a CB1 contact, respectively, thereby placing each register stage into its reset condition.

The initial application of a ground request signal pulse on the left store line 51 also places the first register stage 34(0) intoits set condition. This pulse momentarily applied ground to the AB/4 relay coil by way of a relay contact AAZ (relay AA/3 being energized), line 38(0), contact AA] and diode 48(0), the energization of the AB/4 relay coil in turn causing its ABI contact to transfer to provide a ground holding circuit to maintain that relay in an energized condition through line 49(0). The energization of the AB/4 relay coil in turn causes the transferred A84 contact to provide a ground holding circuit to maintain the CL/3 relay energized; the charge on capacitor 58 maintains the CL/3 relay energized until this ground holding circuit is established.

Additional ground pulses provided on the left store line SI serve to cause additional register stages to assume a set condition, in a manner similar to that for the first register stage, the left register l8 being a shift register comprising stages 34(0), 34( b) and 34(c). For example, an additional ground pulse request signal on the left store line 51 is connected to an input line 38(b) of the register stage 34(b) by means of an AA3 contact (the AA/3 relay coil being de-energized), and a HA2 relay contact (the BA/4 relay coil being energized). In a manner similar to that described earlier, the register 34(b) assumes a set condition, its BB/l relay becoming energized, and the BA/4 relay becoming de-energized. Similarly, still another ground pulse on the left store line 51 serves to cause the third register stage 34(0) to assume a set condition by energization or operation of a CB/l relay 37(0), the ground pulse being applied to the last register stage by means of contacts AA3 and BA3 to an input line 38(c) of that register stage.

The storing of request signals representative of teller calls into the right register 19 is accomplished in a manner identical to that just described for the left register 18. Request signals on lines 22 (FIG. 1) are applied to a right store line 62 (FIG. 2), and serve to energize a relay coil CR/3 designated by reference numeral 63 from a power input terminal 64 through a series conneeted surge resistor 66 and a diode 67 when a capacitor 68, connected in parallel with the CR/3 relay, is charged to the effective operating voltage of that relay. A right register power line 69 provides power to the commonly connected terminals or lines (not shown) of right register stages upon transfer of a CR] contact to a power input terminal 7|. A request signal supplied to the right store line 62 also serves to place the first right register stage into a set condition, that set condition causing a relay contact 72 to transfer to provide a ground holding circuit for the CR/3 relay, capacitor 68 maintaining energization of that relay prior to transfer of contact 72.

The left and right register stages I8 and 19 are provided with left and right clear lines 73 and 74 (FIGS. 2 and 3) respectively, the interconnection between the right clear line 74 and the right register stages being omitted for simplification. A ground pulse on a clear line 73, 74 serves to effect cancellation of the last stored request signal in a register.

Assuming that request signals are stored in all of the illustrated register stages of the left register 18 (the relays AB/4, BB/] and CB/l shown in FIG. 2 being energized), a request signal cancel or ground pulse on the left clear line 73 is connected through a contact CA4, a line 76 and a contact CA2 to the input line 38(() and, when applied through a contact CAI, serves to shortcircuit and de-energize the CB/] relay through a diode 46(0), thereby resetting register stage 34(c). The deenergized condition of the CB/I relay serves to effect transfer of the CB1 contact to its rest position in order to ground the CAM relay coil through line 43(0), the CAM relay becoming energized upon termination of the clear or cancel pulse.

In response to energization of the CA/4 relay (FIG. 2), the left clear line 73 is extended to the next register stage 34(b) by means of a line 77, an additional request signal cancel or ground pulse on the left clear line 73 serving to reset that register stage. In response to deenergization of the BB/I relay, and energization of the BA/4 relay, the left clear line 73 is extended to the first register stage 34(0) through a line 78, a ground pulse on the left clear line serving to reset the first register stage by means of contacts ABZ and AA2, in a manner similar to that described earlier for the other register stages. When the last request signal has been cancelled from the left register 18, the release of the AB/4 relay opens the A84 contact. which serves to de-energize the CL/3 relay. The cancellation of request signals from the right register 19 is accomplished in an identical manner.

FIG. 3 is a schematic diagram which illustrates the features of the sequencer 17 shown in FIG. 1. The sequencer 17 comprises switching means, preferably eIectro-mechanical relays, for selectively energizing the instructing means, and includes additional switching means, also preferably electro-mechanical relays, for providing a request signal cancel pulse to each regster following energization of its associated instructing neans, as will be described in detail.

As noted earlier, the dispatching system circuit com- :irises a control switch 16 (FIG. I) operatively preconiitioned upon storage of request signals to initiate op- :ration of the sequencer. FIG. 4 illustrates a treadleperated version of the control switch 16. FIG. 5 illusrates an electronic timer version of the control switch l6 for initiating operation of the sequencer at regular ireselected time intervals in response to storage of nultiple request signals in either or both of the registers l8 and I9, the timer being operable to control opera ion of the sequencer to maintain instructing means or 8 indicator actuation for a preselected time interval. Either the treadIe-operatcd (FIG. 4) or timer (FIG. 5) version of the control switch I6 can be interchangeably utilized with the sequencer shown in FIG. 3.

The operation of the various components of the dispatching system circuit will become apparent from descriptions of its various operating conditions. Assuming that request signals have been stored in the left register 18, no request signals being stored in the right register 19, the energized condition of the AB/4 relay (FIG. 2) serves to connect voltage to the connected version of the control switch 16. As shown in FIG. 4, closure of an AB3 contact for the left register 18 serves to connect voltage from the power input terminal 79 to the treadle-operated switch 81 or other switching means operated in response to the presence of a unit to be dispatched, in turn connected to one terminal of a TT/4 relay 82 having another input terminal connected to ground. Closure of the treadle-operated switch 81 energizes the TT/4 relay upon charging of its. parallelconnected capacitor 83 to the operating voltage of that relay after a time delay, the energization of the TT/4 relay initiating operation of the sequencer.

With reference to FIG. 3, the sequencer comprises an MM/3 relay 84, an LR/Z relay 86 operable to control energization of the right indicator, the MM/3 and the LR/Z relays being connected to the right register power line 69. The sequencer further comprises an LL/Z relay 87 operable to control energization of the left indicator sign 13 (FIGS. 1 and 6), the LL/2 relay being connected to the left register power line 61. The sequencer 17 also includes a PA/Z relay 88 and a PB/4 relay 89 interconnected in a circuit operable in a manner to be described.

The energization of the TT/4 relay by operation of the treadle-operated switch 81 (FIG. 4) causes its associated contacts TTl (FIG. 3), TT2 (FIG. 3), TT3 (FIG. 6) and TT4 (FIG. 5) to transfer. The TT4 relay contact is utilized, as described later, only with the timer version of the control switch, its transfer having no effect in the presently described operating condition in which the treadIe-operated switch 81 is utilized. Relay contact TTI (FIG. 3) transfers in order to ground an MM3 contact of the MM/3 relay by means ofa line 91, again with no effect. Relay contact TT2 (FIG. 3) transfers in order to apply ground to the LL/Z relay 87 through a line 92, an MMI contact, a line 93, a PA2 contact, a line 94, a PB4 contact, a line 96, a PB3 contact, a line 97, and an isolating diode 98 to energize the LL/2 relay, that relay having been previously connected to the left register power line 61 which was energized upon closure of the CLI contact to the power input terminal 59 (FIG. 2) upon transfer of the (IL/3 relay, as described earlier.

Upon energization of the LL/2 relay (FIG. 3), the left indicator 13, which preferably comprises a direction indicating sign, is energized. With reference to FIG. 6, a left indicator lamp in the left indicator 13 is energized from a I20 volt A.C. power supply at terminals 99 and 101 over a line I02, a closed contact, a line 103, the closed TT3 contact and a line 104, the transfer of the TT3 contact also serving to illuminate a station available lamp 106 in order to indicate the availability of a serving station.

With reference to FIG. 7, the energization of the LL/2 relay also serves to energize a chime circuit 106 to provide an audible signal from an A.C. power supply at terminals 107 and 108. on the order of I211 volts A.C., over a line 109, a line 111, the closed LL2 contact. and a line 112.

It will be noted from FIG. 3 that the MM] contact routes the ground condition from the transferred TT2 contact to the LL/2 relay to operate the left indicator sign instead of the LR/2 relay for operating the right indicator sign.

In response to opening the treadle-operated switch 81 (FIG. 4). the TT/4 relay is maintained in an energized condition for a predetermined time delay determined by the value of the capacitor 83 in order to maintain the left indicator sign energized for a slight time interval after the dispatched customer or unit moves out of the entrance station and toward the left set of serving stations 11, in order to prevent confusing instructions resulting from an immediate additional closure of the switch 81.

When relay TT/4 (FIG. 4) becomes de-energized, its associated relay contacts TF1, TT2, TT3 and TT4 return to their rest positions. Contact TTI (FIG. 3) transfers with no apparent effect. Contact TT2 (FIG. 3) returns to its rest position to apply a request signal cancel or ground pulse to the left clear line 73 through a line 113 and a CR3 relay contact (in its rest position since the right register has no stored request signals). The ground pulse on the left clear line 73 serves to cancel a request signal in the left register following actuation of its associated left indicator 13.

With reference to FIG. 5, a timer circuit, generally illustrated by reference numeral 114, is energized from a power input terminal 116 upon closure of the AB3 contact of the left register, to supply power to a line 117. Line 117 is connected through a resistor 118 to supply power to the TT/4 relay 119 for energizing the latter upon charging of its associated capacitor 121 to the operating voltage of that relay in a manner identical to that described earlier with respect to the TT/4 relay 82 utilized in the treadle/operated version of the control switch 16.

Upon transfer of the TT/4 relay (FIG. its associated relay contact TTl (FIG. 3) transfers to remove ground from a capacitor 122 (FIG. 5) transfers to remove ground from a capacitor 122 (FIG. 5) through a line 123, thereby enabling capacitor 122 to become charged through a resistor 124 and a variable resistor 126, the latter being adjustable to vary the charging time of capacitor 122 and hence the duration of the time interval during which the TT/4 relay is energized. A wiper contact 127 of the variable resistor 126 is connected to an emitter terminal 128 ofa unijunction transistor generally designated by reference numeral 129, in turn connected to line 117 through a resistor 131, and to a ground line 132 through a resistor 133. Resistor 133 in turn is connected to a gate lead 134 of an SCR 136 through a resistor 137, the gate lead 134 being connected to line 132 through a resistor 138. The SCR 136 is connected in parallel with the TT/4 relay through the TT4 contact and a resistor 139.

When the emitter 128 of the unijunction transistor 129 reaches the transistor firing voltage, transistor 129 then discharges capacitor 122 through line 132 and resistor 133, thereby causing the voltage on the gate lead 134 of the SCR 136 to rapidly rise to a level sufficient to gate or trigger the SCR into conduction to shortcircuit the coil of the TT/4 relay, causing that relay to become de-energized. For the voltages and component values illustrated in the figures. a desirable setting of the adjustable resistor 127 provides a preferred timer on or operating period of approximately five seconds (during which the TT/4 relay is energized), and an off period of approximately one second while capacitor 121 is recharging to the operating voltage level of the TT/4 relay (during which the TT/4 relay is deenergized) provided that multiple request signals are stored in the left register 18. The timer I14 repeatedly initiates operation of the sequencer 17 (by way of contact TT2) at regular preselected time intervals. and is further operable to control operation of the sequencer 17 to maintain actuation of the indicator sign for a preselected time interval. The timer repeatedly initiates operation of the sequencer 17 until all of the request signals stored in the left register 18 are cancelled. The timer operates in an identical manner in response to storage of request signals in the right register 19.

Assuming now that request signals are stored in the right register 19, with no request signals stored in the left register 18, the energization of the (R/3 relay (FIG. 2) serves to energize the right register power line 69 from the power terminal 71, as previously described, to supply power to the MM/3 and the LR/2 relays (FIG. 3). The closure of an AB3 relay contact for the right register serves to enable energization of the TT/4 relay by operation of either the treadle-operated switch 81 (FIG. 4) or the timer 114 (FIG. 5), depending upon which version of the control switch is connected, as previously described.

Upon energization of the TT/4 relay for either the treadle-operated version (FIG. 4) or the timer version (FIG. 5) of the control switch 16, relays contact TTl (FIG. 3) transfers to ground the MM3 contact through line 91, with no effect for the present operating condition. Relay contact TT2 (FIG. 3) transfers to supply ground to energize the MM/3 relay through line 92, the closed relay contact CLZ and a line 141, the LR/Z relay also being energized through a line 142, an isolating diode 143 and a line 144. The energization of the MM/3 relay serves to transfer the MMI contact to provide a ground holding circuit to a line 146 connected to line 142 to maintain the MM/3 and the LR/2 relays energized.

With reference to FIG. 6, energization of the LR/2 relay serves to close the LR] contact to energize a right indicator lamp in the right indicator 14 from the power input terminals 99 and 101 over line 102. line 103, the closed TT3 contact and line 104. As shown in FIG. 7, the chime circuit 106 is energized from the power input terminals 107 and 108 by the closure of the LRZ contact in a manner identical to that described earlier.

Upon de-energization of the TT/4 relay, contact TT2 (FIG. 3) transfers to provide a ground pulse to the right clear line 74 through line 113, a line 147 and the CL3 contact (no request signals being stored in the left register) in order to cancel the last stored request signal in a right register stage.

As shown in FIG. 3, the LR/Z relay is connected by means ofline 144 through a diode 148 to a line 149 and a capacitor 151, this capacitor in turn being connected to the right register power line 69 for a purpose to be described subsequently.

If request signals are entered into the left register 18 while the right indicator 14 is operating (that is while the MM/3, LR/Z and TT/4 relays are energized), and

with multiple request signals already stored in the right register 19, it will be seen that the sequencer I7 is operable to prevent interference with the energizing circuit for the right indicator upon entry of request signals into the left register. the sequencer being further operable to alternately control actuation of both indicators 13 and 14 in response to the simultaneous storage of re quest signals in both the registers 18 and 19.

When request signals are entered into the left register 18, the CL/3 relay (FIG. 2) transfers upon charging of capacitor 58, as described earlier. causing contacts CLl (FIG. 2). CL2 (FIG. 3) and CL3 (FIG. 3) to transfer. Relay contact CLZ opens the ground connection supplied to the energized relay MM/3 through the TT2 contact (the TT/4 relay being energized). line 92 and line 141; however. an alternate ground path to maintain the MM/3 and the LR/2 relays energized is provided by the MM] contact now connecting line 92 to line 142 through line 146, and to line 144 through iso lating diode 143. Thus. the MM/3 relay operation provides lockout switching means for preventing interference with the energizing circuit for the right indicator 14 by entry of request signals produced by the left set of serving stations 11 associated with the non-energized left indicator 13.

The closure of the CLI (FIG. 2) contact provides power to the left register power line 61 which. in turn. is connected by way of a CR2 contact (FIG. 3) to a line 152 connected to relays PA/Z and PB/4 through resistors I53 and 154, respectively. Line 152 is energized in response to the closures of both relay contacts CLl and CR2 because of the simultaneous storage of request signals in both registers 18 and 19. For this condition. the PB/4 relay 89 becomes energized through the resistor 154, a line 156 connected to the MM3 contact (the MM/3 relay being energized). line 91 and the now closed TTI contact. Upon energization of the PB/4 relay. a PBI contact transfers to ground line 156 to maintain that relay in an energized condition. Isolating diodes 157, 158, I59 and 161 are provided for isolating the operation of the PA/Z and PB/4 relays.

When the TT/4 relay is de-energized as previously described. its associated contacts return to their rest positions. Contact TTI (FIG. 3) removes ground from the MM3 contact connected to line 91, with no effect. Contact TT2 (FIG. 3) transfers to remove ground from contact MMl, thereby causing the simultaneous release or de-energization of relays MM/3 and LR/Z (the latter causing the right indicator 14 to become deenergized). Relay contact TT2 provides a request signal cancel pulse or ground condition on the right clear line 74 through line 113, line 147, the PB2 contact. a line 162 and the CL3 contact (the CL/3 relay being energized). causing the cancellation of the last entered request signal in the right register 19. It is seen that the sequencer 17 comprises switching means for providing a request signal cancel pulse to the right register 19 following energization of the instructing means or indicator 14 associated therewith.

Upon further TT/4 relay operation in respnse to actuation of either the treadlecperated switch 81 or the timer 114, its associated contacts transfer. Relay contact TTI (FIG. 3) transfers to ground the MM3 contact, in turn grounding the junction of diodes 157 and 158 through a line 163 and a PA! contact, causing the FEM relay to become de-energized. its associated contacts returning to their rest positions. Relay contact TT2 grounds the LL/2 relay by means of line 92, the MMI contact. line 93, the PAZ contact. line 94, the PB4 contact. line 96, the P83 Contact. line 97 and the diode 98 to energize the relay (which was previously connected to the left register power line 61 through the closed relay contact CL] The energization of the LL/Z relay causes actuation of the left indicator I3 and the chime circuit 106 as previously described.

When the time TT/4 relay is tie-energized. its associated contacts TTI, TT2, and TT4 transfer to their rest positions. Relay contact TT2 (FIG. 3) removes ground from the LL/2 relay. thereby causing it to become deenergized to terminate energization of the left indicator 13 and the chime circuit 106. The TT2 contact applies ground by way of line 113, line 147, contact P132, line 162, the MM2 contact, a line 163 and the CR3 contact to the left clear line 73 to cancel the request signal last stored in the left register 18. The relay contact TTI (FIG. 3) transfers to remove ground from the junction of diodes 157 and 158 by way of line 91, the MM3 contact. and line 163, causing relay PA/Z to become energized from line 152 through resistor 153, a line 164 and the P81 contact. thereby causing the transfer of contacts PA] and PA2.

When the TT/4 relay becomes energized again. relay contact TTI applies ground to the transferred PAI contact. through contact MM3, thereby causing the PB/4 relay coil to become grounded and energized. with resultant transfer of contacts PBI, PBZ, P83 and P134, contact PB] providing a holding circuit to maintain relay PB/4 energized. Relay contact TT2 transfers to ground. and therefore energizes the LR/2 relay by way of line 92, contact MM], contact PA2, a line 166, the contact PB4, line 96, the contact P83, line 149 and diode 148. The energized LR/2 relay operates the right indicator I4 and the chime 106. The MM/3 relay does not operate for this condition.

When the TT/4 relay is de-energized. contact TTl removes ground from the PAl contact. causing the PAl/2 relay to become de-energized, with resultant transfer of contacts PAI and PAZ to their rest positions. Contact TT2 transfers to provide a ground on the right clear line 74 through line 113, line 147, the P82 contact. line 162 and the CL3 contact.

The alternate actuation of the left and right registers 18 and 19 repeatedly occurs, as long as request signals are simultaneously stored in both registers. It is seen that for this simultaneous request signal storage. when both the PA/2 and PB/4 relays are de-energized, the left indicator 13 is operated. Conversely. when the PA/2 and the PB/4 relays are energized. the right indicator I4 is energized. The energized PA/Z relay (and its associated contact connections) causes operation of the right indicator 14, a de-energized condition of the PA/2 relay causing the left indicator 13 to operate. An energized condition of the PB/4 relay (and its associated contact connections) effects cancellation of the last stored request signal in the right register 19, a deenergized condition of the PB/4 relay causing cancella tion of the last stored request signal in the left register 18.

Assuming that the last request signal was cancelled from the right register 19, contact 72 (FIG. 2) opens in response to de-energization of its associated relay coil (not shown) in the right register. causing relay CR/3 to become de-energized after a time delay during which capacitor 68 sufficiently discharges to the dropout voltage of that relay. with resultant transfers of contacts CR1, CR2 and CR3 to their rest positions. CR1 (FIG. 2) transfers to open the supply circuit through the right register power line 69 to the MM/3 and the LR/Z relays. CR2 (FIG. 3) opens the supply circuit to line I52 from the left register power line 6I, causing deenergization of the FEM relay. The CR3 contact (FIG. 3) transfers to its rest position to provide a path from the TT2 contact to the left clear line 73 by way of line 113. The dispatching system circuit will continue to operate in response to storage of request signals in the left register 18.

When the TT/4 relay is again energized. the TTI (FIG. 3) contact transfers to ground the MM3 contact through line H with no effect. The TT2 (FIG. 3) contact transfers to cause the LL/2 relay to become grounded. and therefore energized. by way of line 92, contact MMI, line 93, the PA2 contact. line 94, the PB4 contact. line 96, the P83 contact, line 97 and diode 98, as described earlier. The energized LL/Z relay causes operation of the left indicator l3 and the chime I06.

When the TT/4 relay is de-energized. the TT2 contact transfers to apply a request signal cancel pulse to the left clear line 73 through line 113 and the CR3 contact to cancel the last stored request signal in the left register. The operation of the dispatching system circuit 10 continues until all of the request signals stored in the left register are cancelled.

If request signals are entered into the right register I9 while the left indicator 13 is operating (that is. while the LL/2 and TT/4 relays are energized). and with multiple request signals already stored in the left register I8, the sequencer I7 is operable to prevent interference with the energizing circuit for the left register I3 upon entry of request signals into the right register, the sequencer being further operable to alternately control actuation or energization of both indicators I3 and I4 in response to the simultaneous storage of request signals in both the registers I8 and 19.

Entry of request signals into the right register I9 causes transfer of the CR/3 relay (FIG. 2) upon sufficient charging of its associated capacitor 68, with resultant transfers of contacts CR1 (FIG. 2). CR2 (FIG. 3). and CR3 (FIG. 3). The transfer of contact CRI applies battery to the right register power line 69 which is connected to the MM/3 and the LR/2 relays; but energization of these relays is prevented by operation of the now open CLZ contact (FIG. 3) of the CL/3 relay (the CL/3 relay being energized). this contact providing a lockout switching means for preventing interference with the energizing circuit for the left indicator 13 upon entry of request signals produced by the right set of serving stations I2 associated with the nonenergized right indicator 14. The transfer of the CR2 contact energizes line I52 from the left register power line 61 to supply power to the PA/Z and the FEM relays, which remain file-energized.

When the TT/4 relay is de-energized. the TTI contact removes the ground connection to the PA/Z coil by way of line 91, the MM3 Contact, line 163 and diode I57, thereby causing the PA/2 relay coil to become energized by way of line 152, resistor I53, line 164 and the FBI contact. The TT2 contact transfers to remove ground from the LL/2 relay. the ground circuit to the LL/Z relay having also been broken by the transfer of the PA2 contact. The TT2 contact also supplies a request signal cancel pulse or ground to the left clear line 73 by way of line 113, line I47, the PB2 contact. line 162, the MM2 contact. line I63 and the CR3 contact.

Upon re-energization of the TT/4 relay. the TTI contact transfers to ground the FEM relay by way of line 91. the MM3 contact. line 163, the PA] contact and diode I6I. causing the FEM relay to become energized with resultant transfer of its associated PBI, P82, PB3 and PB4 contacts. The TT2 contact transfers to ground and therefore energizes the LR/2 relay through line 92, the MMI contact. line 93, the PA2 contact. line 166, the PB4 contact. line 96 of the PBS contact. line 149 and the diode 148. The energization of the LR/Z relay, causes actuation of the right indicator l4 and the chime circuit 106.

When the TT/4 relay becomes die-energized. the TTI contact transfers to remove ground potential from the PA/2 relay causing it to become de-energized. The PB/4 relay remains energized by its ground holding circuit through contact PB] and line I56. The TT2 contact transfers to de-energize the LR/Z relay, the ground circuit to that relay being also interrupted by the transfer of the PA2 contact. The transfer of the TT2 contact also supplies a ground pulse to the right clear line 74 by way of line II3, line I47, the P82 contact. line I62 and the CL3 contact.

When the TT/4 relay is again energized. the TTI contact transfers to supply ground to the junction of the diodes 157 and 158 through line 91, the PAI contact, the line I63 and the MM3 contact. thereby causing the PB/4 relay to become de-energized and release. The TT2 contact transfers to apply ground to the LL/2 relay by way ofline 92, the MMI contact. line 93, the PA2 contact, line 94, the P84 contact. line 96, the PB3 contact, line 97 and the diode 98. The energization of the LL/2 relay causes the left indicator I3 and the chime 106 to become energized.

When the TT/4 relay is de-energized again. the re moval of the ground potential from the junction of diodes 157 and I58 by the transfer of the TTI contact causes the PA/2 relay to become energized from the line I52 through resistor 153, line 164 and the FBI contact. The TT2 contact transfers to cancel a request signal in the left register 18 by way of line I13, line 147. the P82 contact, line I62, the MM2 contact. line I63 and the CR3 contact.

The alternate actuation of the left and right registers I8 and I9 continues until all of the request signals are cancelled from one of the registers. Assuming that the last request signal has been cancelled from the left register IS, the contact AB4 of the left register (FIG. 2) opens to cause the CL/3 relay to become de-energized upon sufficient discharge of its associated capacitor 58, with resultant transfers of the CLI, CL2 and CL3 contacts to their rest positions. The CLI contact transfers to open the supply circuit to the left register power line 61, which terminates the supply to the LL/2 relay. and also to the PA/2 and PB/4 relays which (as noted earlier) operate only when request signals are stored in both registers. The dispatching system circuit I0 will continue to operate in response to storage of request signals in the right register 19, in a manner similar to that described earlier. Capacitor I51 (FIG. 3) prevents momentary loss of operation of the LR/2 relay upon de-energization ofthe PA/Z and PB/4 relays until a new ground path for the LR/2 relay is provided by the MMI contact.

With reference to FIG. I again, it will be noted that the control circuit relationships between the sequencer I7 and the left register 18 and its associated left register, represented by the request signal storage line 23 and the power control line 24, respectively, are accomplished by the CL/3 (FIG. 2) and the LL/2 (FIG. 3) relays and their associated contact connections. The re' quest signal storage line 26 and the power control line 27 similarly represent the operation of the CR/3 (FIG. 2) and the LR/Z (FIG. 3) relays and their associated contact connections, respectively. The request signal cancellation lines 28 and 29 to the left and right registers. respectively, represent operation of the TTZ, CR3, CL3, P82 and MMZ contacts and their associated connections shown in FIG. 3. The control switch 16 is in control circuit relationship with the sequencer 17, as shown in FIG. 1 by line 31, this line representing the operation of the TT2 contact. The request signal storage lines 32 and 33, connected from the left and right registers, respectively, to the control switch 16, represent the operation of the AB3 contacts (FIGS. 4 and 5) associated with relays in the left and right registers.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it is apparent that various changes may be made in the form, construction, and arrangement of its component parts without departing from the spirit and scope of the invention or sacrificing all ofits material advantages, the form described being merely a preferred embodiment thereof.

We claim:

I. For use in a dispatching system having actuating means at each of two sets of serving stations for pro ducing electrical request signals, and having two electrically actuated instructing means each for an associated set, a circuit comprising: control switch means, sequencing means and two register means, each said register means being associated with an instructing means, and being connected to the actuating means at an associated set of serving stations to store the request signals produced thereby, said sequencing means being in control circuit with each said register means and the instructing means associated therewith and being operable to control actuation of the latter in response to storage of request signals in said register means, said sequencing means being operable to alternately control actuation of both instructing means in response to simultaneous storage of request signals in both said register means, said sequencing means being further operable to cancel a request signal in a said register means following each actuation of its associated instructing means, said control switch means being in control circuit with said sequencing means and each said register means and being preconditioned upon storage of request signals to initiate operation of said sequencing means; whereby said circuit effects actuation of an instructing means in response to storage of a request signal produced by actuating means at its associated set of serving stations, and effects alternate actuation of both instructing means in response to simultaneous storage of request signals produced by actuating means at both sets of serving stations.

2. The circuit of claim 1, wherein said control switch is operated in response to the presence of a unit to be dispatched.

3. The circuit of claim 2, wherein said control switch is treadle-operated.

4. The circuit of claim I, wherein said control switch means comprises an electronic timer for initiating operation of said sequencing means at regular preselected time intervals in response to storage of multiple request signals in said register means.

5. The circuit of claim 4, wherein said timer is further operable to control operation of said sequencing means to maintain instructing means actuation for a preselected time interval.

6. The circuit of claim I, wherein said sequencing means comprises switching means for selectively energizing the instructing means, additional switching means for providing a request signal cancel pulse to each register means following energization of the instructing means associated therewith, and lockout switching means for preventing interference with the energizing circuit for an actuated instructing means by entry of request signals produced by the set of serving stations associated with the non-actuated instructing means.

7. The circuit of claim 6, wherein said switching means comprise electromechanical relays.

8. The circuit of claim I, wherein each said register means comprises a shift register having plural bistable multivibrator stages.

9. The circuit of claim 8, wherein each of said stages comprises a steering relay and a stabilizing relay both in circuit with a control input and a common terminal, said steering relay being energized upon application of a predetermined voltage to said terminal, energization of said steering relay serving to switch said input to said stabilizing relay for energization of the latter in response to a ground pulse at said input, deenergization of said steering relay serving to precondition deenergization of said stabilizing relay and re-energization of said steering relay in response to an additional ground pulse at said input, said stabilizing relay being operable to provide a ground holding circuit to maintain one of said relays in an energized condition and the other of said relays in a de-energized condition until energization of the latter; whereby said relays are individually and alternately energized in response to ground pulses at said input.

I0. A bistable multivibrator comprising a steering relay and a stabilizing relay both in circuit with a control input and a common terminal, said steering relay being energized upon application of a voltage source to said terminal, energization of said steering relay serving to switch said input to said stabilizing relay for energization of the latter in response to a ground pulse at said input, de-energization of said steering relay serving to precondition de'energization of said stabilizing relay and re-energization of said steering relay in response to an additional ground pulse at said input, said stabilizing relay being operable to provide a ground holding circuit to maintain one of said relays in an energized con dition and the other of said relays in a de-energized condition until energization of the latter, whereby said relays are individually and alternately energized in response to ground pulses at said input.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. I 3,893,097

DATED July 1, 1975 |NVENT0R(5) I Ronald Louis Lach and William Jean Brier It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 5, lines 24 and 25, "de-enerization" should be -de-energization--.

Col. 10, line 3, on should be on".

Col. 10, line 4, off should be --"off".

Col. 10, line 34, "relays" should be relay--.

Col. 11, line 60, "respnse" should be response-.

Col. 16, lines 48 through 64, delete claim 10.

Signed and Sealed this sixteenth D21) of September 1975 [SEAL] Attesr:

RUTH C. MASON C. MARSHALL DANN Alrestr'ng Officer Commissioner of Parents and Trademarks

Claims (10)

1. For use in a dispatching system having actuating means at each of two sets of serving stations for producing electrical request signals, and having two electrically actuated instructing means each for an associated set, a circuit comprising: control switch means, sequencing means and two register means, each said register means being associated with an instructing means, and being connected to the actuating means at an associated set of serving stations to store the request signals produced thereby, said sequencing means being in control circuit with each said register means and the instructing means associated therewith and being operable to control actuation of the latter in response to storage of request signals in said register means, said sequencing means being operable to alternately control actuation of both instructing means in response to simultaneous storage of request signals in both said register means, said sequencing means being further operable to cancel a request signal in a said register means following each actuation of its associated instructing means, said control switch means being in control circuit with said sequencing means and each said register means and being preconditioned upon storage of request signals to initiate operation of said sequencing means; whereby said circuit effects actuation of an instructing means in response to storage of a request signal produced by actuating means at its associated set of serving stations, and effects alternate actuation of both instructing means in response to simultaneous storage of request signals produced by actuating means at both sets of serving stations.

2. The circuit of claim 1, wherein said control switch is operated in response to the presence of a unit to be dispatched.

3. The circuit of claim 2, wherein said control switch is treadle-operated.

4. The circuit of claim 1, wherein said control switch means comprises an electronic timer for initiating operation of said sequencing means at regular preselected time intervals in response to storage of multiple request signals in said register means.

5. The circuit of claim 4, wherein said timer is further operable to control operation of said sequencing means to maintain instructing means actuation for a preselected time interval.

6. The circuit of claim 1, wherein said sequencing means comprises switching means for selectively energizing the instructing means, additional switching means for providing a request signal cancel pulse to each register means following energization of the instructing means associated therewith, and lockout switching means for preventing interference with the energizing circuit for an actuated instructing means by entry of request signals produced by the set of serving stations associated with the non-actuated instructing means.

7. The circuit of claim 6, wherein said switching means comprise electromechanical relays.

8. The circuit of claim 1, wherein each said register means comprises a shift register having plural bistable multivibrator stages.

9. The circuit of claim 8, wherein each of said stages comprises a steering relay and a stabilizing relay both in circuit with a conTrol input and a common terminal, said steering relay being energized upon application of a predetermined voltage to said terminal, energization of said steering relay serving to switch said input to said stabilizing relay for energization of the latter in response to a ground pulse at said input, deenergization of said steering relay serving to precondition deenergization of said stabilizing relay and re-energization of said steering relay in response to an additional ground pulse at said input, said stabilizing relay being operable to provide a ground holding circuit to maintain one of said relays in an energized condition and the other of said relays in a de-energized condition until energization of the latter; whereby said relays are individually and alternately energized in response to ground pulses at said input.

10. A bistable multivibrator comprising a steering relay and a stabilizing relay both in circuit with a control input and a common terminal, said steering relay being energized upon application of a voltage source to said terminal, energization of said steering relay serving to switch said input to said stabilizing relay for energization of the latter in response to a ground pulse at said input, de-energization of said steering relay serving to precondition de-energization of said stabilizing relay and re-energization of said steering relay in response to an additional ground pulse at said input, said stabilizing relay being operable to provide a ground holding circuit to maintain one of said relays in an energized condition and the other of said relays in a de-energized condition until energization of the latter, whereby said relays are individually and alternately energized in response to ground pulses at said input.

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