US1934685A

US1934685A - Multiplex signaling system

Info

Publication number: US1934685A
Application number: US622347A
Authority: US
Inventors: Charles S Demarest
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1932-07-13
Filing date: 1932-07-13
Publication date: 1933-11-14
Anticipated expiration: 1950-11-14

Description

Nov. 14, 1933. c.1s. DEMAREST 1,934,685

MULTIPLEX SIGNALING SYSTEM Filed Juiy 13, 19:52 :5 Sheets-Sheet 1 INVENTOR 6'. (ifiemai agt ATTQRNEY 1 9 C. s. DEMARESTE 1,934,635

ATTORNEY 14, 1933- c. s. DEMAREST MULTIPLEX SIGNALING SYSTEM '3 SheeteSheet 3 Filed July 15, 1932 FTP I INVENTOR C. $.Dermaresj BY ATTORNEY terns.

@atented Nov. 14, 1933 TED STATES PATET OFFEE MULTIPLEX SIGNALING srs'rarr Application my 13, 1932. Serial No. 622,347

12 Claims.

This invention relates to signaling systems and to synchronous switching arrangements for such systems and to means for providing start-stop operation or multiplex operation in signaling sys- In synchronous switching systems at the present time the means employed to provide successive separate transmission paths is ordinarily a mechanically rotated distributor at the transmitbe shown more fully in the following detailed description.

The invention may be more fully understood from the following description together with the accompanying drawings in the Figures 1, 2 and 3 of which the invention is illustrated. Fig. 1 is a circuit diagram embodying one form of the invention. Figs. 2 and 3 are circuit diagrams showing modifications of the invention. Similar ref- W ting end of a circuit operated in synchronism erence characters have been utilized to denote 65 with a similar device at the receiving end. These distributors at any instant provide a complete circuit through brushes and contact elements which is distinct from the circuit completed an instant later through difierent contact elements on each distributor. Common uses of such devices include means for multiplex telephone signaling and for certain types of telegraph service. A number of separate signals are transmitted in each revolution of the distributor brush to identify each character transmitted. These distributors may be rotated at high speeds so that 'a large number of separate signals may be transmitted.

Various means are employed for synchronizing the distributors at the two ends of a circuit. In start-stop operation the distributor brushes are normally held unoperated until the start signal is applied at the sending end, after which one revolution of the sending distributor is permitted and the brush is again stopped. The start signal is also transmitted to the receiving end followed by thesuccessive signals corresponding to the condition of the distributor bars swept over in each revolution. At the receiving end the start signal releases the distributor brush, permitting one revolution, and the successive signals are impressed/on the corresponding bars of the distributor. By operating both distributors at approximately the same speed the lack of synchronism in one revolution is negligibl For continuous operation of the distributors a synchronizing channel separate from the signaling channels may be employed or other means for holding synchronism locally without transmitting a separate signal therefor.

In the arrangements disclosed in this invention the mechanically rotated distributors are replaced like parts in all of the figures.

Figs. 1 and 2 show circuit arrangements for providing start-stop operation. Since the sending and receiving apparatus and circuits are identical only one end of the circuit is shown in these figures. Synchronism of the sending and receiving circuits is provided by adjustment of the corresponding timing elements in the synchronizing circuits at each end of the circuit.

Fig. 1 shows an arrangement in which the application of the start signal causes the apparatus to operate through one cycle and stop until the start signal is again applied. The signals transmitted over the various channels during the cycle will depend upon the condition of the corresponding sending keys Kl, K2, etc. These are shown here as separate keys but may be contacts operated, for instance, by a master key which closes certain of these contacts to transmit a desired sequence of signals. Printing telegraph equip- 8! .ment might also be used to control these keys.

predetermined interval after the cycle of operations has been stopped.

Fig. 3 shows a continuously operating system in which synchronism is controlled to a very high degree of accuracy by the continuous transmission of a separate synchronizing signal of a frequency difierent from that of the channel signals.

In Fig. 1 is shown an arrangement of gas-filled 10 tubes in two general groups: The first group, S1, S2 SN, performing the functions of closing and opening the separate transmission paths in addition to aiding in the synchronization, and the second, Sn, S1, S2, etc., being used only for 0 synchronizing purposes. These tubes are so interconnected that the line circuit is normally held open until the start signal is transmitted, whereupon voltage is applied to the input circuits of all the tubes S1, S2, SN. Tube S1 operates immediately and operates S1, which, after a predetermined interval, quenches S1 and shortly thereafter operates S2. The operation of S: causes the operation of S2, which in turn quenches S1 and then after an interval operates a succeeding tube similar to $1. This sequence continues until Sn is. operated. This tube quenches the start tube S1,, removing power from the inputs of S1, S2, etc., and also the auxiliary tubes S1", S2, etc. After the desired interval Sn quenches itself and the circuit is restored to normal, ready for the next start signal. A start signal is also transmitted to the distant end of the circuit at the time it is transmitted to the tubes at the sending end and the closing and opening of the various transmission paths through tubes S1, S2 S11 is duplicated in identical fashion at the receiving end. If the sending keys are closed or open the corresponding signal or lack of signal will be received on the proper channels provided the adjustment of the operation and quenching of corresponding tubes is closely enough in synchronism at the two ends of the circuit. As the condition of the various sendin keys changes for each cycle of operation different groups of signal impulses corresponding to different characters are received. 7

In Fig. 1 the gas-filled thermionic tubes each consists of a filament or heater 1 energized by a battery 2, a cathode 3, grid 4 and anode or plate 5 enclosed in an envelope containing gas at the desired pressure. The gaseous content of the tube might, for example, be neon. In this figure the start signal is transmitted by closing key 6 momentarily. Current from the alternating current source 7 is .then transmitted through key 6 to winding 8 of transformer T1. and at the same time over leads L in the line circuit to the corresponding winding 8 of transformer T1. at the receiving end of the line circuit. The current through winding 8 induces a voltage in winding 9 which is applied between grid and cathode of tube 81., through the tuned circuit consisting of inductance 10 and condenser 11 in parallel and battery 12. The tuned circuit is tuned to the frequency of the alternating current supplied to the anode circuit in order to prevent this frequency from aiiecting the grid circuit of the tube. Battery 12 is provided to hold the grid of S1. normally more negative than the ionizing voltage of the tube; The application of the voltage from winding 9 is sumcient to drive the grid in the positive direction to cause ionization of the gas present. Anode voltage is supplied by battery 13, the plate current flowing, when the tube ionizes, from battery 13 through resistance 14, choke coils 15, and the anode-cathode arc path in the tube. Resistance 14 is adjusted to limit the current flow to the value requiredto maintain the arc. When the arc is established the resistance of the anode-cathode path drops from a very high to a very low value, thus effectively closing a circuit through transformers 16 and i7 and condenser 18. This condenser is provided to open the circuit to direct current to prevent short-circuiting battery 13. When this circuit is closed voltage from the alternating current source 20 r is transmitted through

transformers

16 and 17 to leads 21 and 22. Tube S1. remains ionized until the end of the cycle of operations to be -hereinafter described. Consequently, the voltage supplied to these two sets of leads is continuous until that time. The voltage on leads 21 is applied to the input circuits of tubes S1, S2 S11 simultaneously, but as described below tubes S2 Sn are arranged not to operate on this input alone. Tube S1, however, is arranged to ionize a predetermined time after tube S1. has been operated as will be hereinafter pointed out. The ionization of S1 closes the line circuit through lead 23, winding 24 of transformer T1, condensers 25, the anode-cathode arc path-of tube S1, tuned circuit 26 and lead 27 to the other side of line L. S1 remains ionized until quenched by tube S1'-, as described below. The operation of tube S1 occurs as follows: Voltage from leads 21 isimpressed through transformer 28 on the input circuit consisting of rectifier 29, resistance 30 and condenser 31. Due to the constants of the rectifier, condenser and resistance the voltage across condenser 31 builds up until the grid potential reaches the point at which ionization of tube S1 occurs. This causes the tube S1 to operate a predetermined time after the operation of tube Sr. Tuned circuit 32 is provided to prevent operation of S1 by the alternating current supplied to the anode circuit.

When tube S1 has ionized, the circuit through

transformers

34 and 35 and condenser 36 is closed. The condenser serves the same purpose as the corresponding unit 18 associated with tube 81.. Voltage from source 38 is then transmitted through the transformers to the input circuit of tube S1 which ionizes immediately and remains ionized until theend of the cycle of operations when it is quenched by tube Sn. Upon the ionization of S1 the voltage on leads 22 which is supplied by source 20 through tube SL, as described above, is applied through transformers 39 and 40 to the rectifier circuits associated with tubes S1 and S2. Rectifier 41, resistance 42 and condenser 43, associated with the anode circuit of tube S1 are so adjusted as to build up a voltage across the condensers which opposes the voltage of battery 46 and reduces the effective anode voltage of tube S1 below that required to maintain the arc, thus quenching S1 and opening the heretofore described signal transmission path throughthis tube after the desired transmitting interval has elapsed. Resistances 44 are provided to dissipate the charge on condenser 43 after the alternating current voltage is removed when tube S1 is quenched. Resistance 45 limits the anode current from battery 46. Choke coils 47 are provided to ofler a high impedance to alternating current of either the frequency of source 38 or source 20. At the same time that voltage is being applied to the circuit of rectifier 41 it is also applied to the circuit consisting of rectifier 48, resistance 49 and condenser 50 associated with the grid circuit of tube S1. The voltage across condenser 50 builds up to apply positive voltage to the grid of S2, opposing the voltage of battery 53. However, tube S2 will not ionize due'to this input alone, but requires the combined inputs of rectifiers 48 and 54. The voltage across condenser 56 has already been built up to its maximumvalue from the voltage applied by leads 21 during the time of operation of tube S1. The constants of resistance 49 and condenser 50 are so chosen that tube S: will ionize shortly after tube 81 has been quenched by the action of rectifier 41 described above. This closes the line circuit from one side of line L through lead 23, winding 58 of transformer T1, condensers 59, the arc path of tube S2, tuned circuit 60 and lead 2'7 to the other side of line L. Under this condition voltage from the alternating current source 61 5 is supplied to tube 82' in a manner similar to that described for tubes S1 and S1 and S2 ionizes and remains ionized until the end of the cycle of operations. Tube S1 is quenched after the desired transmission interval and succeeding sets of tubes are ionized shortly thereafter inthe same manner as described for tube 81,- and so on until tube S11 is .in turn ionized, closing the transmission path from one side of line L through lead 23, winding 62 of transformer TN, conden- 15 sers 63, the arc path of tube SN, tuned circuit 64 and lead 2'7 to the other side of line L.

Upon the ionization of tube SN the voltage supplied by source 65 is transmitted through transformers 66 and 6'7 to leads 68. This volta e is applied to the rectifier'circuit associated with tube S1.. Rectifier 69, resistance '70 and condenser '71 are so adjusted that the voltage across the condenser opposes the voltage of battery 13, thus quenching tube S1.. Resistances '72 are provided to dissipate the charge on condenser 1'71 when the voltage from leads 68 is removed by the quenching of Sn. The adjustment of resistance '70 and condenser '71 is such as to cause tube S1. to quench shortlyafter tube Sn ionizes. The voltage on leads 68 is also impressed at the same time on the rectifier circuits associated with tubes S1, S2, etc., causing these tubes to be quenched also, but after the quenching of 51., so that tube S1 will not again ionize upon the quenching of S1. Voltage from-leads 68 is also impressed upon rectifier '73 associated with the anode circuit of tube SN, and resistance '74 and condenser '75 are so adjusted that S11 will be quenched after both S1. and the auxiliary tubes S1, S2, etc., have been quenched and after the desired transmission interval has elapsed. This completes the cycle of operations and restores the circuit to the normal condition when it may be restarted by momentarily closing the starting 45 y 6- During the cycle of operations just described the line circuit has been closed successively at each end of the circuit through

transmission paths

1, 2, 3 N in succession. The signals 5 transmitted over each separate path are dependent upon' whether keys K1, K2 Kn are operated or released. If these keys are operated signals are transmitted from the alternating current signal source '79 through windings 80 of transformers 1 1,11; Tn, over the line circuit and are received at the other end of the to obtain repeated operation. The operation of the various tubes S1. S2 Sn and the auxiliary tubes S1, S1, etc., is the same as described in connection with Fig. 1. Upon operation of tube S11 voltages will be applied to leads 68 as before from source 65. The voltage on these leads is applied to the rectifier circuit of tube S1. to quench this tube as before and also to the rectifier circuits of tubes S1, S2, etc., to quench these tubes following the quenching of S1.. In this arrangement, however, the voltage on lead 88 is also applied to the grid circuit rectifier of an additional tube S'r whose purpose is to quench Sn and also to restart the cycle. The detailed operation is as follows: The voltage on leads 68 is applied through transformer 82 to rectifier 83, resistance 84 and. condenser 85 and ma predetermined time causes the ionization of tube S'r. When this occurs volt-. age from source 88 is applied through transformers 89 and 90 to the rectifier circuits associated with the plate circuits of tubes Sn and ST. The adjustment of rectifier '73, resistance '74 and condenser 75 is such as to quench tube Sn after transmission path N has been closed for the desired time. The adjustment of rectifier 9i, resistance 92 and condenser 93 is such that tube Sr is quenched shortly after tube SN has been quenched. However, since tube SN is quenched after S1. and S1, S2 etc., and thus removes the quenching voltage from the plate circuit rectifier of tube $1., the voltage from source 88 applied through transformers 89 and 97 to the winding 98 of transformer Tr. will rte-ionize tube Sr. and start a new 100 cycle. Tube Sr is arranged to be self-quenching v shortly after the new cycle is started.

Fig. 3 shows an arrangement for continuous operation in which the synchronization is controlled by a separate synchronizing signal of a different frequency from the channel signals. Filters F1 and F2 are provided to confine these two frequencies to the proper channels. In this arrangement which uses tube circuits somewhat similar to those described in conneetionwith Figs. 1 and 2, the input rectifier circuits are so adjusted that ionization will occuronly when the peak value of the synchronizing voltage isreached or when spurts of interrupted high frequency current are trans mitted. In this way successive operation of the tubes S1, S2, etc., may be very accurately spaced and synchronized with the corresponding tubes at the receiving end of the circuit.

As shown in Fig. 3 a line L connects twosimilar groups of gas-filled tubes S1, S2 SN arranged to be used as either transmitting or receiving elements. Filters F1 and F2 are provided to separate the synchronizing frequency from-the signal frequency. At the sending end the closing of key 6 transmits alternating current of frequency F1 from the source '7 and interrupter 7' through transformer 8 to leads 9 which are connected to the grid circuits of the various tubes S1, S2 Six. The grid circuits of tubes S2 SN are so adjusted that they will cause ionization at the peak values of the signal voltage only when an additional input is received from the preceding auxiliary tubes S1,

S2, etc. When the synchronizing voltage is first applied by the closing of key 6 it is applied to tube S1 through potentiometer 10 and transformer 35 11 to the grid circuit which consists of rectifier 12, resistance 13, condenser 14, battery 15 and a tuned circuit containing a coil 16 and condenser 1'7. Thealternating current received from the synchronizing source '7 is rectified by rectifier 12 1 and builds up a charge on condenser 14 which is applied between the cathode and grid of tube S1. Battery 15 is provided to hold the grid 4 normally more negative than the value required to ionize tube S1 so that the tube will not be operated until the peak value of synchronizing voltage is applied. The tuned circuit is provided to prevent alternating current applied to the anode circuit from afiecting the grid circuit. By adjusting the potentiometer 10 and the values of tube S1 is de-ionized before tube S2 is ionized to resistance 13 and condenser 14 the tube may be made to ionize only at the peak value of the synchronizing voltage.

When tube S1 ionizes, the arc path resistance between the anode 5 and cathode 3 drops from a very high to a very low value and effectively closes a circuit consisting of one side of line L, lead 18, coil 19 of filter F1, lead 20, winding 21 of transformer T1, condenser 22', the arc path of tube S1, condenser 23, tuned circuit 24, lead 25, coil 26 of filter F1, lead 2'! and the other side of line L. At the time when key 6 is closed the synchronizing frequency is also transmitted from source 7 through condensers 28 of filter F1 to the line L and thence to the receiving end of the circuit where it passes through the corresponding filter F1 to transformer 8 and to the input circuit of tube S1 at the receiving station. The adjustments of the tube circuits at the receiving end are identical with those at the transmitting 'end so that the corresponding tubes will ionize and close the circuit through their are paths at the same time that these paths are closed at the sending end. Under the conditions for tube S1 if key K1 is closed, a current of frequency F1 from source 30 will flow through winding 81 of transformer T1, causing current to flow through the circuit described above and inducing a voltage in winding 32 of the receiving transformer T1. This causes the current to flow through the rectifier 33 to the receiving device R1 which may be of any well known form.

The plate potential of tube S1 is provided by battery 35 which is applied through chokes 36 and resistance 37 between the cathode and anode.

When the tube ionizes as described above, thepath consisting of the arcpath of the tube, condenser 38 and the windings of transformers 39 and 40 is closedand power is then supplied by the alternating'current source 41- through transformers 39 and 40 to the grid circuit of S1. Condenser 38 is provided to prevent short-circuiting battery 35. t

When alternating current is applied to transformer 39 and thence to the grid circuit of tube S1 through tuned circuit 43 and battery 44,this tube ionizes immediately, its plate voltage being supplied by battery 45 through chokes 46 and resistance '7. Alternating current from the source 48 is transmitted through transformers 49 and 50 over leads'51 to the rectifier 52. Resistance 53 and condenser 54 are so proportioned that the charge built up on condenser 54 requires a predetermined time to reach such a value that tube S1 is quenched. This time is determined so that prevent both paths being closed in parallel. Resistances 55 are provided to limit the rate at which condenser 54 discharges during the nega- .up to a maximum at each peak of the rectifier input voltage. After tubes S1 and S1 have been operated and alternating current is transmitted through transformer 57 and potentiometer 58 to rectifier 64, resistance 65 and condenser 66, the

voltage drop across resistance 67 added to the peak .value of charge on condenser 63 is sufficient to operate S2.

Tube S1 is ionized shortly after tube S1 has been quenched as described above and closes a path through winding 68 of transformer T2, condenser 69, the cathode-anode path through the tube condenser 70 and tuned circuit 71. The line circuit is then closed through tube S: in place of tube S1 and a signal will be transmitted over line L to the far end depending upon the condition of switch K2. At that time the corresponding tubes at the far end of the line have been operated in a manneridentical with that described for the transmitting end. The signal transmitted through switch K2 will be received through transformer T1 at the receiving end rectified by rectifier unit 73 and operate receiving device R1.

The quenching of S1 through the operation of S1 and the subsequent operation of other similar sets of tubes, will occur in a manner similar to that described above for S1 and S2. Since the auxiliary tubes S1, S2, etc., remain ionized until the end of the cycle, tubes S1, S2, etc., are prevented from ionizing twice during a complete cycle upon successive peaks of signaling voltage. When Sn is operated, closingthe circuit through TN, and transmitting the signal determined by the condition of key Kn, the alternating current supplied by source 75 will be transmitted through transformers 76 and '77 and leads 78 to-the rectifiers associated with the plate circuits of all the auxiliary tubes S1, S2", etc. Thus, in connection with tube S1, rectifier 179, resistance 80 and condenser 81 are arranged to build up a voltage across the condenser to oppose-the voltage of battery 45 so that tube S1 will be quenched. Tube S2 and other corresponding tubes are quenched in a similar manner. 7

Voltage from source 75 is also applied to leads 88 and thus to rectifier 84, resistance 85 and condenser 86 to provide a voltage opposing the voltage of battery 88, thus quenching tube Sn. Resistance 85 and condenser 86 are so propertive half cycle of voltage applied to the rectifier @ped that tube S1: is not quenched until all from source 48. Tube S1 will continue in the ionized state until the entire cycle of operations has been performed and the quenching voltage istransmitted from tube Sn to all the auxiliary tubes. The continued ionization of S1 prevents S1 from ionizing again during the same cycle.

Power is also transmitted from source 48 through transformers 49 and 50 and leads 56 to the rectifier circuit associated with-the grid of tube S1. The grid circuit of this tube has two rectifier circuits connected in seriel, the adju'stments of

potentiometers

58 and 59 being arranged so that neither rectifier alone will provide sufiicient voltage to cause ionization of the tube. Thus tube 8: is prevented from roperating'until of the auxiliary tubes have been quenched.

When tube S1" has been quenched tube S1 is again permitted to be ionized by the synchronizing signals from source 7, providing key 6 is still closed. In this case the same cycle of operation will occur.

While the arrangements described are particularly adapted to start-stop or multiplex operation of signaling systems the principles disclosed are adaptable to other uses. Accordingly, while the invention has been described as embodied in certain specific arrangements, it is understood that it may be used in various forms without departing from the scope of the-appended claims.

What is claimed is:

1. A multiplex signaling system comprising a transmission line, a series-of gas filled discharge tubes, means associated with said line for successively rendering the grids of said discharge tubes less negative with respect to their cathodes whereby the tubes of said series will operate in succession, and means controlled by the ionization of each of said tubes for completing indilrlilual signaling circuits over said transmission 2. A multiplex signaling system comprising a transmission line, a series of gas filled discharge tubes, means associated with said line for ionizing the gas filled tubes of said series successively, means controlled by the ionization of each of said tubes for completing individual signaling circuits over said transmission line, and means controlled by the ionization oflthe last tube of said series for restoring the tubes of said series to a normal condition of deenergization.

3. A multiplex signaling system comprising a transmission line, a series of gas filled discharge tubes, means associated with said line for successively rendering the grids of said discharge tubes less negative with respect to their cathodes whereby the tubes of said series will operate in succession, means for deenergizing each of'the tubes of said series before the succeeding tube has been ionized, and means controlled by the ionization of each of said tubes for completing a signaling circuit over said transmission line.

4. A multiplex signaling system comprising a transmission line, a series of gas filled discharge tubes, means associated with said line for ionizing the gas filled tubes of said series successively, means for deenergizing each of the tubes of said series before the succeeding tube has been ionized,

and means controlled by the ionization of the last tube of said series for restoring said appahas been ionized, means for maintaining said deenergized tubes in a condition of deenergization, means operative when each of the tubes of said series is ionized for completing individual signaling circuits over said transmission line, and meanscontrolled by the ionization of the last tube of said series for restoring said apparatus to its original condition.

6. A multiplex signaling system comprising a transmission line, a series of sets of gas filled tubes, each of said sets comprising a first tube adapted upon ionization to ionize a second, tube in said set, switching means associated with said line for applying a voltage to said line and to the grids of the first tube in each of said sets of tubes whereby the first tube of the first set of said tubes will be ionized, means responsive to the ionization of the second tube-of said first set for extinguishing the first tube of said first of the first tubes of each of said sets of for completing individual signaling circuits over said transmission line. a

7. A multiplex signaling system comprising a transmission line, a series of sets of gas filled tubes, each of said sets comprising a first tube adapted upon ionization to ionize a second tube in saidset, switching means associated with said line for applying a voltage to said line and to the grids of the first tube in each of said sets of tubes whereby the first tube of the first set of said tubes will be ionized, means responsive to the ionization of the second tube of said first set for extinguishing the first tube of said first set and for applying a voltage to the grid of the first tube of the succeeding set of tubes to ionize said last mentioned first tube, means responsive.

'to the ionization of the second tube of said last mentioned set for extinguishing the first tube of said set and for applying a voltage to the grid of the first tube of the next succeeding set oftubes to operate said last mentioned first tube, means responsive to the ionization of the first tube of the last of said sets of tubes in said series for causing the deenergization of each of the second tubes in each set of tubes of said series, and means controlled by the ionization of each of the first tubes of each of said sets of tubes for completing individual signaling circuits over said transmission line. f, r

8. A multiplex signaling system comprising a transmission line, a series of gas filled discharge tubes, switching means associated with said line for ionizing the gas filled tubes of said series successively, means for deenergizing each of the tubes of said series before the succeeding tube has been ionized, means for maintaining said deenergized tubes in a condition of deenergization, means operative when each of the tubes of said series is ionized for completing individual signaling circuits over said transmission line, and

means controlled by the ionization of the last tube of said series for restoring said apparatus to its original condition and for subsequently reoperating said switching means to cause a re'pe-- tition of said cycle of operations with respect to'igo said tubes.

9. A multiplex signaling system comprising a transmission line, a gas filled discharge tube associated with said line for controlling the operation of said signaling system, switching means for applying to said line and to the grid of said control tubea voltage to cause the ionization of said control tube, a series of gas filled discharge tubes, means operative upon the ionization of said control tube for ionizing the gas filled tubes of 30 said series successively, means for deenergizing each of the tubes of said series before the succeedingtube has been ionized, means operative when each of the tubes of said series is ionized for completing individual signaling circuits over said transmission line, and means controlled by the ionization of the last tube of said series for restoring the tubes of said series to their original condition'and for deenergizing said control tube. 10. A multiplex signaling system comprising a transmission line, a gas. filled discharge a tube associated with said line for controlling the operation of said signaling system, switching means for applying to said line and to .the grid of said control tube a voltage to cause the ionization of 145 said control tube, a series of gas filled discharge tubes, means operative upon the ionization of said control tube for ionizing the gas filled tubes of said series successively, means for deenergizing each of the tubes of said series before 150 ative when each 01' the tubes of said series is ionized for completing individual signalingcircuits over said transmission line, an additional discharge tube ionized upon the operation of the last tube of said series of tubes, and means con-= trolled by the ionization of said additional tube for restoring the tubes of said series to their original condition, for deenergizing said control tube, for subsequently ionizing said control tube to initiate a cyclic repetition of said operation of said series of tubes, and for subsequently causing its own deenergization.

. 11. A multiplex signaling system comprising a transmission line extending from a sending station to areceiving station, a series of gas filled discharge tubes at said sending station, a similar series of gas filled discharge tubes at said receiving station, switching means associated with said line for successively ionizing the gas filled tubes of each of said series of tubes, means for deenergizing each of said tubes in each of said series of tubes before the succeeding tube therein has been ionized, means operative when corresponding tubes in each of said series of tubes are ionized for completing individual signaling circuits over said transmission line.

12. A multiplex signaling system comprising a cessively ionizing the gas filled tubes oi. each of said series of tubes, said synchronizing operating voltage being produced by spurts of high frequency current applied to said line and to the input circuits oi the tubes of said series and said tube input circuits being adjusted so that said tubes will become ionized only upon the application to said input circuits of said operating intermittent synchronizing voltage, means for deenergizing each of the tubes in each of said series of tubes before the succeeding tube therein has been ionized, and means operative when corresponding tubes in each of said series of tubes are ionized for completing individual signaling circuits over said transmission line.

CHARLES S. DEMAREST.