US2038649A - Selective signaling system - Google Patents

Description

April 28, 1936.

c. s. DEMAREST SELECTIVE SIGNALING SYSTEM Filedfict. 13, 1932 EQES wan Shaun; MW

T INVENTOR C. 5. Den Lowest BY v ATTORNEY Patented Apr. 1936 PATENT OFFICE SELECTIVE SIGNALING srs'mu Charles "Sidney Demarest, Ridgewood, N. J., as

signor to American Telephone and Telegraphv Company, a corporation of New York Application October 13, 1932, SerlalNo. 637,650 3 Claims. wr'm-sas) This invention relates to-electrical circuits, and more particularly to circuits for selecting signaling or switching, in which a signal may be transmitted selectively'to one of a plurality of circuits or a circuit may be connected selectively to one of a plurality of, circuits.

Such arrangements have heretofore been provided by the use of electromagnetically operated relays or selector switches, involving mechanical motion of some parts thereof. These moving parts have required careful adjustment and maintenance and troubles have also been experienced at the points of electrical contact as films of dirt or corrosion may impair the electrical contact to such an extent that the circuit becomes noisy or actually is not completed. It is an object of this invention to provide means whereby such selective switching or signaling operations may be carried out without the use of electro-mechanical devices such as relays or selectors. I have described such a system in my copending application, Serial No, 629,382, filed August 18, 1932, Patent No. 1,908,326, from which this invention is differentiated by the method of selection employed. In the above mentioned application, selection is made by the use of a train of coded impulses. In this inventiomhowever,

I have utilized electrical tuned circuits, together with a source ofsignaling current of adjustable frequency, so that by sending currentpf a ticular frequency one of a plurality or circuits is selected. Obviously, it would be possible to combine the features of this invention with that already referred to so as to increase the number of stations or circuits available for selection, the

first selection being made by selecting the proper frequency, after which "coded impulses of this frequency select a particular circuit from the I. indicatesthe subscribers station and its associated line conductors 2 and 3, connecting it to the gas-filled tube switching equipment at the central oflice. Tubes 4" and 5 are so -arranged that line conductors 2 and 3 are normally connected to the conductorsSB and 96 of line 0 through the arc paths of these tub'es. Grid batteries 1 for these two tubes are poled so that the established. Thus if none of the keys Ki are operated, a cbnnection may be established'between the subscribers station I and an operator over lines 96 and 96'. Signaling impulses are sent from keys K; to KN over conductors 21 and 28,. the current for such impulses being supplied 5 by the vacuum tube oscillator composed of vacuum tube 30, output transformer 29, conmined frequency to be transmitted over signal ing pairs 2'! and 28. Obviously these conductors 21 and 28 might be the same conductors as 2' and 3, separation of the selecting currents from the iiiother currents transmitted over conductors 2 and 3 being made by proper choice of selecting frequencies and the provision of suitable filters. An untuned transformer I8 is connected with-its primary bridgedacross the signaling pair and 2d its secondary connected to the grid and cathode of gas-filled tube}, IS. The grid ofthis tube is normally biased negatively by battery' I I. It should be noted that the same reference characterhas been used for batteries, coils and the like as of id entical function associated with different pa of the circuit. Upon the application of any sig "a1ing current of frequency F1 ,to Fn, an arc will be establishe tube l9. Upon'the striking of this arc, current will flow from "alternator 22 10 to the primary of transformer 16. Current will flow from the secondary thereof through theprlmaries of transformers-l3 and in. parallel, over conductors l6 and I5, through condenser 2|,

anode of tube l9,'th1f0ugh the arc to the cathode, 35 I and thence through condenser 20 back to the secondary of transformer l6. {the secondaries of transformers l3 and M are connected to the rectifier resistance units II and I2 in the-"anode;

circuits of tubes 4 and 5. These rectifiers areiso 40- poled that the resulting electromotive force across the resistance elements will'oppose the anode batteries 8 and extinguish the arc in the tubes 4 and 5, thus disconnecting line 0. Choke .coils l0 and resonant circuits 9 keep the alternating/1i current from generator 22 out of the transmission circuit over conductors 2 and 3. At the same time the signaling current applied over conductors 21. v and 28, which is of one of N predetermined frequencies F1 to FN will actuate the corresponding 50 set of connector tubes, of whichonly one set,

' the F1 group, has been indicated in the drawing.

Supposing that the frequency sentout is'Fi, due, to operation of key K1 at thestation,thecondepser C1 will be connectedto the oscillator coil 3 l and 0111- 55 i rent of frequency F1 will be applied to conductors 21 and 28. This current will be passed by selective network 32, but rejected by all others. As a rest'rit, in addition to quenching tubes 4 and 5 as hereinbefore explained, alternating current from vacuum tube oscillator 30 will be applied to the primary of transformer 33 and the voltages induced in the secondaries of this transformer will cause arcs to be established in gas-filled tubes 34 and 35, the positive half cycles being suificient to override the effect of biasing batteries 11. When the arcs have struck it is apparent from the drawing that a circuit is established from conductors 2and 3 to conductors 52 and 52 of line I.

If another key, say K3, be now pressed, a double connection toiboth lines I and 3 would be established. If, however, it is desired .to establish another siiTgle connection, key KN must first be op- I erated sending out frequency Fa. It will be apparent that tube 42 will be operated, as voltage of this frequency Fa will be applied to the grid of tube 42' through selective network 40 and transformer 4|. Direct current will flow from battery 3 through inductance 5|, resistance 45 to the anode'of tube 42, through the arc thereof and back to battery 8. At the same time an A. C. path from generator 50 will be completed through the primary of transformer 49, condenser 48, the arc path of tube 42 and back to generator 50. Alternating current will flow from the secondary of transformer. over conductors 25 and 25, to rectifier resistance network 24, and will after rectification build up a direct potential opposing the anode battery of tube l9, thereby quenching this tube and permitting gas-filled tubes 4 and 5 to' again establish an arc, thus restoring the connection to'line 0. 'At the same time alternating current will flow from conductors 25 and 26 into the primaries of transformers 38 and 39. The anode circuits of the connector tubes 34 and 35 contain rectifier and resistance elements 36 and 31, connected to the secondaries of transformers 38 and 39. The direct potential built up'a'cross the resistances of these rectifier-resistance units will oppose the anode batteries of tubes '34 and 35 and thus quench the arcs therein, so disconnecting conductors 2 and 3 from line I.

At the same time transformer 41 has supplied an A. C. potential to rectifier 43, and this will slowly charge up condenser 46, through resistance 44, and in such a manner as to oppose the voltage of the anode battery 8 of'tube 42. After a period predetermined by the amplitude of the I voltage supplied from the secondary of transl possible. 5-

former 41, the'values of resistances 44, 45 and of capacity 46, this voltage will be sufficient together with the potential of the negative half cycles of the alternating voltage to' quench the arc in tube 42. The system is thus restored completely to its normal condition.

It isobvious that conductors 21 and 28 could be made the same as conductors 2 and 3 as above stated by providing additional filtering. If'this is done, the signaling current from generator 30 may be applied to the circuits 0, I, etc., selected on a frequency basis. If now these line conductors be arranged to serve as the input circuit to a selective system of the-type shown in my above identified patent, and if pulsesof the frequency sent out by generator 30 be sent, instead of a single signal, selection of further lines maybe made on' a coded impulse basis, making it pos- While this invention has been" described with regard to a particular embodiment thereof, it is not to be regarded as limited to the specific arrangements disclosed, but includes any and all organizations falling within the scope and spirit of the appended claims.

What is claimed is:

1. In a signaling system, selectively operated switching means comprisin'ga plurality of gasfilled tube devices each having input and output circuits, each of said devices having plate voltages suflicient 'to maintain the devices in discharging condition after they are initially broken down and started in discharging condition, extinguishing means associated with the output circuits of each of said tube devices for changing said plate voltages so that they will be insufiicient to maintain the devices in discharging condition, the first of said gas-filled tube devices being normally adjusted to be in a discharging condition, filtering devices adapted to transmit different frequencies associated with the input circuits of all of said tube devices except said first tube'device, a multifrequency source, switching means for applying currents of different frequencies from said source to said filtering devices to selectively cause the discharge of said tube devices, means directly controlled by any of the currents from said source for operating the extinguishing means associated with said first gas-filled tube device-switching means for v applying current of a definite frequency from said source to the last one of said gas-filled tube devices to cause the operation of said last tube device, and means controlled by the operation of said last tube device for operating the extinguishing devices associated with filled tube devices each having input and output 40 circuits, each of said devices having plate voltages suflicient to maintain the' devices in discharging I, condition after they are initially broken down and started in discharging condition, extinguishing means associated with the output circuits of each of said tube devices for changing said plate voltages so that they will be insufiicient to maintain the devices in discharging condition, the first of said gas-filled tube devices beingnorinally adiusted to be in a discharging condition, filtering devices adapted to transmit different frequencies associated with the input circuits of all ofsaid tube devices except said first tube device, a multifrequency source, switching means for applying currents of different frequencies from said source to said filtering devices to selectively cause the discharge of said tube devices, means directly controlled by any of the currents from said source for operating the extinguishing means associated with said first gas-filled tube device, switching" means for applying current of a definite frequency from said source to the last one of said gas-filled tube devices to cause .the operation of said last tube device, means controlled by the operation of said last tube device for operating the exting'uis g devices associated with all of said tube devices except said first-tube device, and r slow-operating means associated with and controlling the operation of the extinguishing means of said last one of said gas-fi1led tube devices.

3. In a signaling system, selectively operated switching means comprising a plurality of gasfilled tube devices each having input and output circuits, each of said devices having plate voltages sufiicient to maintain the devices in discharging condition after theyare initially broken down and started in discharging condition extinguishing means associated with the output circuitsot each of said tube devices for changing said plate voltages so that they will be insumcient to maintain the devices in discharging condition, the first of said gas-filled tube devices being normally adjusted to be in a discharging condition, filtering 'devices adapted to transmit diflerent frequencies associated with the input circuits of all of said tube devices except said first tube device, a multifrequency source, switching means for applying currents of difierent frequencies from said source to said filtering devices to selectively cause the discharge of said tube devices, an auxiliary gasfilled tube device for controlling the extinguishing means of said first normally operated gas! said auxiliary gas-filled tube device, switching means. for applying current 01. a definite frequency from said source to one of said gas-filled tube devices to cause the operation of said last mentioned tube device, and means controlled by the operation of said last tube device for causing the operation of the extinguishing devices associated with said auxiliary gas-filled tube and CHARLES S. DEMARES'I'.

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