US2008563A - Electrical selector system - Google Patents

Description

July 16, 1935l M. D. SARBEY 2,008,563

ELECTRICAL SELECTOR SYSTEM Filed Dec. 15, 1935 3 Sheets-Sheet 1 f il) A a.. N.. G L mw J 4 4 m :u u T U a nl mm Ii. a \.,J T., U k J Fa f ...51V All. C. 'Il v W1 n. Rw w.. Rm m. Rm 1MB k T... c. T: s j. Q .w 6 .z R w C: Il V M. F .AI... ||uH U ma r, 4 .u M :..W n" 4 ...luv H. G -.5 n f. n kw Wm n.. ,mm v r.. 5 2 W A .v m a. F n 1 ||||L .I l I I I -......lllm

M. D. sARBEY ELECTRICAL SELECTOR SYSTEM Filed Dec. 1s, 193s July 16, 1935l Hyj- Inventor l /Vnwe/E 3 Sheets-Sheet 2 maynz'ade 0f incwm'ny signal:

l?. E Amplifier l Il il ll'il Al'torney July 16, 1935.

M. D. SARBEY ELECTRICAL SELECTOR SYSTEM 3 Sheets-Sheet 5 Filed Dec. 13, 1933 3gp 'W Tfr v v kar :z I .e

Urn: fo calldfubnrter.: or Group:

l Patented July 1.6, 1935 l l t UNITED :STATES PATENT `OFFICE ELECTRICAL sELECTon :SYSTEM v Maurice Sarbey, Bay Village, Ohio Application December 13, 19st, serial No. 702,267

\ ze claims. (Crus-za) This invention relates to electrical controlsysatedl and thosel noty operated, and causing the tems, and particularly to control systems adapt- Vdevice operated nearest to the line of division to ed to the conveyance of independentv diilerentiput` out of operation all, of the others operated.,

ated control pulses over a single channel, each Still a. further object of the invention is to pulse being a complete signal. apply to a,sing1e wire a succession of electrical 5 An object of the invention is to convey along a pulses of -varying electrical magnitude, to convey single channel a sequence of electrical pulses, the pulses t0 enOlfheIpOiIlt, and there apply the each signal pulse being a complete signal adaptsuccessive pulses in sequence t0 a pluralityof ed to produce differentiated results at a remote responsive devices, the respective devices being receiving point. v Operable by vpulses of different magnitude, eaehrlo Still another object t of this invention is to disdevice being adapted to put out of operation .those tinguish differentsignal pulses in terms of the devices which are operable byv lower magnitude magnitudes thereof for the production of `different DlllSeS-o I e effects at a, receiving point, Still another object of the invention isito con- A furtherobject of this invention is to initiate vey over a cable single electrical pulses of nonat a transmitting ypoint a plurality of signals of significant or uniform time duration and of sigdiiierent electrical magnitude; to convey the significant electrieel magnitude furthe conveyance nais along a single channel; and to translate the of intelligible signals, which may be 'utilized for vvarying magnitudes 4into varying responses at a o the operation of a printing telegraph.

receiving point.` Another object of the invention is to transmit 20 Another object ofthe invention is to transmit over a single line a plurality of electrical pulses over a single wirel circuit a plurality of electricall of nonsigniiicant time duration and signiilcant 1 pulses in. sequence, successive pulses having dit- .electrical magnitude at low, closely spaced elecferent electrical magnitudes; and to translate the trical magnitudes, tor amplify the electrical magrespective magnitudes into predetermined renitudes to higher values and increase the spac- 25 sponses at a receiving'point. ings there-between. and thereafter -to utilizethe Another object4 Yoi? the vinvention is to operate e amplied electrical magnitudes for the operation Vany one of a plurality of devices selectively lby of predetermined magnitude responsive devices,

means of the electrical magnitude of a signal, each different signal magnitudecausing the opthe signal magnitude being sufficient to operate eration of a. single predetermined device. y l 30 a predetermined device and those devices oper` `Still another object oi the invention is to opableby a lesser signal magnitude being prevented rerate a typewriter at a remote point by means of from operating by the operationv of the predea plurality of single electrical pulses of nonsigtermined device. l niilcant time duration and of signicant elec- 'A stiu further object of the invention is to tricai magnitude, each type key being nierateeiA 35 respectively operable by predetermined signal transmit over a single :wire circuit a plurality of by a current pulsefof a predetermined magnitude electrical pulses of varying electrical magnitude,v diflerent from the magnitudes required for the and to utilize the successive pulses for the selec- Operatin of an if the other keys, tive operation of a plurality of responsive devices Stm luther abject of the invention is to operate a printing telegraph device by `means yoi av plurality o! electrical pulses, the respective types ofthe printing telegraph being selected by choice Another object of the invention is to set up a of the' magnitude or the electrical pulses trans' group of potential vresponsive devices such that at taemgc invention isto tran a given potential applied to the whole group will i ano l t? l; I to u, tels' actuate only one thereof. m t digit se ec ng pu ses as or au ma c e" A further object of the invention is to conphone dwing by pulses of predetermined elec' nect a plurality of electrically responsive devices tric magnitude each die being represented by in parauei to a single circuit for the-application e Single Pulse 0f *i dem@ electric-a1 magnitude 5 simultaneously to ou thereof of a plurality or Still another object of the invention is te in electrical control pulses,` the devices being so arlllete electl'lcl pulses 0f Varying magnitude Wc.' ranged that some may not, be operated by a cordingtothe electricalindicaticn oi aphoto-ce)l, pulse, others may be operated by a pulse, thereby to transmit these pulses to a remote point, and to` producing a line of division between those operoperate a predetermined one of a plurality o! magnitudes, and to render inoperable all the responding devices except the one operable by the signal magnitude transmitted.

vdevices according to the magnitude of the electrical pulse initiated by the photo-cell.

Still another object ofthe invention is to proto use the mechanical or electrical movements directly or to control electricalor other mechanical functions.

In the prior art of signal conveyance, it has been found convenient to convey control signals in a variety of Ways, successive independent pulses being used, such, as for instance, the telegraph code, in which time durations of succesive pulses and spacings are utilized for the conveyance of information, and such as the iive unit code, in

which the presence or absence of pulse at synchronized` intervalsdetermines the character of signals conveyed. Both of these methods involve a determination of-elapsed time in the course of signal transmission which is often undesirable. Other control circuits require a'large number of wires, a separate wire or circuit being provided for each control function. -Still'other control systems utilize relay chains of various forms in which the relays are actuated in succession according to the duration or sequence of the current pulses controlling them.

'I'he device of this invention provides a simple control system in which the information! or control factor is conveyed in terms of electrical magnitude, instead of in terms of time or sequence or relay chains as-in the prior art.

Thus the device of this invention provides means by which a given electrical magnitude may be made to convey a given signal, or to controla given operation while a second slightly dliferent -electrical magnitude carries a different item of information or effects a different control.

That is, broadly, the device of this invention makes it possibleto apply to a` given circuit a certain electrical magnitude, which may be a small number of volts, which, when so applied; by the device of the invention, will actuate a given member; and a second slightly dlil'erent electrical magnitude, a higher or a lower voltage, will actuate a different member; still another voltage will actuate another device and so onover a range of voltage steps, both the number and size of the steps being determined by the insulation resistance of the system, the current carrying capacity, the characteristics of the component parts, and the other usual electrical factors.

The invention may also utilize, in combination with the voltage responsive devices, anampllfying member adapted to increase the magnitude oi electrical values applicable to the device, thereby making it possible to utilize a large number of closely spaced voltage steps at low voltage for transmission, and to increase the magnitude by ampliiication at the receiving device to `insure accuracy of operation.

- ably of direct current.

Fig. 3 is a circuit diagram of a device illustratv ing the invention appliedto a radio signal channel. Y

Fig. 4 is a diagrammatic representation of an embodiment of the invention as applied to the sending and reception of automatic. telephone dialing or pulsing signals.

Fig. 5 'is a diagrammatic representation of an embodiment of the invention, utilizing a photocell for the control or' production of the signal voltage.

The present invention utilizes electrical pulses of different magnitudes for .the conveyance of the desired control or information signal. A single circuit may be used between the sending and receiving points, over which may be conveyed successive electrical pulses for the successive sig-f operation being represented by a pulse of predetermined different voltage. Such signals are conveniently obtained by the closing of keys connected to different points in a chain of series connected batteries, or from keys connected to successive points on a potentiometer resistance energized from any convenient power source, prefer- One end of the potentiometer maybe connected to ground or to a return wire. The several keys are then connected in parallel to a line wire and serve to transmit ov'er -the line wire the desired pulses, controlled in voltage according to the desired signals or actuation to be obtained.

At the remote end of the line wire there is provided a receiving system having a plurality of devices respectively responsive to different voltages, sothat a low voltage will actuate one response device, a higher voltage will actuate another, and a still higher voltage will 'actuate still another, the vnumber of devices, and of different voltages, being determined by the number of signals to be transmitted, or of operations to be obtained.

In view of the fact that a device that is responsive to a given voltage is usually also responsive to higher voltage, the invention provides additional means to prevent the operation of more the actuation of those devices, which are adapted to be actuated by lower voltages.

Simple control system Of the preferred embodiments of the invention herein illustrated and described, the simplest form of the device is shown in Fig. 1. `Referring to this figure, a potentiometer resistance R, is provided through which an electrical current is caused to flow by a source of current, which may be a battery B, or maybe any convenient power source (a direct current generator, or a rectifier). A plurality of taps are connected to the potentiometer vR and lead to the keys K. The other terminals of the keys K are connected to a common lead L, which, in turn, is connected to the line with the positive and negative poles connected, as shown. 'I'he negative end of the potentiometer is grounded at G, as shown, or may be connected to a return line and, for reasons which will later appear, it must be the negative end. It may be noted that the first of the keys K is not connected at the grounded end of the po'- tentiometer resistance R, but is connected at a point a short distance away, so that the closure of the rst key Kl applies a denite voltage between line and ground. Similarly, the closure of key K2 applies a still larger voltage between line and ground and, so on, each key thus applying its characteristic voltage to the line, which voltage may conveniently have values in an arithmetical progression.

At the receiving end the device referred to utilizes a number ofgas discharge devices, which number may be the same as the number of keys K at the sending point. While any gas discharge device which has a control element and a Vcircuit responsive thereto and which has such an operating characteristic that the controlled circuit passes substantially no current until the control element has reached a certain predetermined narrow range of electrical potential, and vvthereafter passes substantially full cunent, may be employed, the gas discharge devices illustrated are of the type known commercially as 'I'llyratron, and consist of an envelope containing a low pressure of vapor, such as mercury, argon,

etc., and a plurality of electrodes consisting of cathode, grid and anode. These devices are of the type which show practically no conductance when the grid is more negative than a s peclc .value and pass full current when the potential on the grid reaches or exceeds in the positive direction the specific or critical value peculiar vto the device.

If, as illustrated, a hot cathode type of gas discharge deviceis used, 'the cathodes of the entire group may be connected in parallel, as is indicated in Fig.' 1, and may be energized from any convenient power source such as an alternating current line, (with a transformer to provide the proper voltage).

t Another potentiometer RR is provided at the vreceiving point, which may also be energized by any convenient power source such as aV battery BB. It may be noted that the poling of this bat-f tery, in common with the battery B at the send.`

ing point is of consequence, the positive end of the battery BB being connected to the grounded end of the potentiometer RR. The successive gas discharge devices Tl to T5, inclusive, asshown, are equipped with connections from the respective grids thereof to successive points on the potentiometer RR. It will be noted that the \sucfcessive points of connection of the grids of the tubes of the gas discharge devices TI to T5, inelusive, are connected successively at more nega` tive points and, accordingly, the respective grids are biased negatively by higher and higher values. Each device T has in its plate circuit a relay member indicated by the reference characters Mi to M5, inclusive.

Each ofthe relays M has two pairs of contacts, one pair being normally closed when. the relay is unenergized, and the other pair being normally open when the relay is unenergized. In addition, the construction of the relays is such that upon energization of the relay, the rst mentioned pair of contacts is opened at once, while the second mentioned pair of contacts is closed only after a brief time delay.

The relays M may be of a solenoid type, as indialso be obvious. of the relay may be increased either by the type cated diagrammatically in Fig. 1, in which the prompt opening of one pair of contacts, and clos- .ing of another pair of contacts after a brief time of winding, the mechanical construction, or by the use of damping rings to obtain the desired delayed action in the latter part of the contact operating stroke. Alternatively, a pair of relays may be utilized, one adapted to open a pair"of contacts upon energizationQwith a minimum of time delay,.the other adapted to close a pair of contacts after a small time delay. In such a system the second relay may be operated from circuit closing contacts on the first relay.

The several plate circuits of the gas discharge devices T are connected through the windings of the several associated relays to the current supply. The normally closed contacts of each relay carry the current for all of the relays in circuit with gas discharge devices having lower negative biases on the grids in such a way as to open. the plate circuits of all the less negatively biased devices when any one operates (except, of course,

the lowest biased device, which has no 'associated' device with a still lower bias). This action is apparent from the diagram of connections shown in Fig. l.

Y The source of anode power for the system illustrated preferably provides alternating current because of the fact that this gives a cessation of current flow during each cycle (the gas discharge device being unilaterally conductive, current does not flow during the reverse half of the cycle). This is advantageous because of the fact that, i! direct current were used with the commercially known Thyratron gas discharge device illustrated, means would be required to interrupt the c urrent flow in the tube, since this gas discharge device does not cease to carry current when the bias upon the grid is returned to its negative value. Obviously if mechanical marginal relays are employed, or gas discharge devices in which the plate current is interrupted when the grid is returned to a negative value, direct current mayl be used in the controlled or anode circuit without the use-of supplemental means for interrupting the flow of current therein. It may be noted that the circuit illustrated is substantially a self-rectifying circuit and each gas discharge device provides its associated relay with rectified current. Because of the requirement that the relay have a fairly steady current in order to complete the delayed latter part of the stroke, the condensers CI to C5 may be included in the circuit to form with the relay winding a simple smoothing lter.-

v G, the several rsistances for the several tubes being indicated at Gi to G5, inclusive. These grid resistors are inserted to limit the grid current, which might otherwise tend to flow when the device becomes conducting. Under such circumstances, the presence of a substantial grid current would cause excess current in the potentiorneter RR, and unbalance the bias voltages.

'Ihe upper contacts of the respective vrelays MI to M5, inclusive, may be utilized for the closing of any desired circuits; alternatively. the movecharge devices T assume the potential set by the points to which they are connected on the potentiometer RR, the relative grid voltagesbeing determined by the relative connection points, and the actual voltages being determined in'addition by the voltage of the battery BB. In normal nonoperated conditionLall of the biases applied to the grids of the several gas discharge devices are more negative than the critical point, and, accordingly, none of the devices pass current; all of the relays M are unenergized, and all of their lower contacts are closed, permitting the application of voltage from the anode power supply source to the respective anodes of the devices.

The closure of a key K applies a positive voltage tothe lead L and to the line, which voltage, in turn, is conveyed by the line to the potentiometer RR.

It will be noted that the common cathode lead of all of the gas discharge devices T is grounded,` thereby setting the potential of the cathode. The positive end of the potentiometer RR is grounded through a line resistor LR. Accordingly, in the absence of a voltage applied to tlie common lead L by vclosure of a key K, the positive end of the potentiometer RR is likewise at ground potential, and all of the grids of the tubes T are at potentials more negative than ground, more negative than the cathodes, and more negative than the line.

I Application oi a given positive voltage to the line by closure of one of the keys K raises the potential of the positive end of the potentiometer RR by an amount depending upon the relative resistance of the line and the resistor LR, and

bearing the same ratioto the applied voltage, that the resistance of LR bears to the combined resistance of the line plus LR. A fixed percentage of the voltage applied to the line thus appears as a voltage drop across the resistor LR and is available to change the over-all potential of the grids of the tubes T with respect to their cathodes.

In the commercial form of gas discharge device, sold under the trade name, Thyratron current ow begins when the grid has approximately the potential of the cathode. In the embodiment shown in Fig. l, the potentiometer drop between the positive end of the potentiometer RR and the point of connection to the grid of the least negatively biased tube is less than the voltage drop, which will be produced across the resistance LR by the lowest voltage applied to the line by closure of one of the keys K. Thus, when key Kl. is closed, a definite voltage, as determined by the potentiometer R, is applied to the line. The voltage drop appearing across thte resistorLR then serves to make more positive all of the voltages delivered to the respective grids by the potentiometer RR. This value, upon closure of the key KI, is adjusted to be sumcient to make the grid of the tube TI positive by a suillcient amount to permit current ow therethrough. 'I'his current flow energizes the relay MI, and closes its contacts to actuate any desired device.

Closure of the key K2 impresses upon the line an appropriately higher positive voltage. which voltage produces an increased drop across the re'- sistor LR, the increase being equal to the difference in bias on the grids of the devices Tl and T2. Accordingly, not only is a positive bias applied to the grid of the tube Tl, but a positive bias is likewise applied to the tube T2, and both become conducting. Both, therefore, energize'thelr respective relays MI and M2. However, the initial rapid actuation of the relay M2 opens its lower contacts,`thereby interrupting the power supply to the tube TI and deenergizing the relay MI before it has completed its full stroke. The relay M2, however, `completes its full stroke, closing its upper contacts to perform the functions desired to be produced by the closure of the key K2.

Closure of `the key K3 gives a correspondingly still higher voltage drop over the resistor LR, which is adjusted to be sufficiently high to bring the grid of the gas discharge device T3 to the positive condition. Current will then start to ilow .through the devices TI to T3. Relay M3 is energized as before indicated for relays MI andyMZ and opens the supply circuit to both devices TI and T2. As previously described this permits the complete operation of relay M3 to close its upper .contacts while deenergizing the relays MI and of gas `discharge devices is limited only by such factors as the permissible circuit voltages across the keys K, thepermissible biases upon the grids of the devices T, and the minimum voltage steps between successive grid biases, and any desired or appropriate number up to the limit set may be utilized. It will be understood that the gas discharge device begins its current conduction at a fairly sharp critical voltage point, but this critical voltage has a small range. The dicrence in the bias of the successive grids must be substantially greater than this smally voltage range. This factor, which is a structural characteristic of the tube is a controlling factor in the closeness of spacing of the taps on the potentiometer RR. In combination with the permissible voltage upon the most strongly negatively biased grid, and themaximum allowable voltage on the devices, which can bey utilized, it determines the maximumy number` of signals which can be transmitted, or the maximum number of operations which can be controlled.

While in the preferred form of the invention just described a particular relay device has been referred to, it is obvious that the invention is operable with any relay device which has a control circuit and a circuit responsive thereto, and which has such an operating characteristic that .the controlled circuit passes substantially nocury system.

passes substantially a full predetermined current. In the preferred embodiments of the invention illustrated and described herein the commercially available gas discharge device sold under the trade name Thyratron has been used as an example, because it has the above operating characteristic. Discharge devices or electronic tubes having this characteristic are referred to herein as of the trigger action type. It will also be apparent that for the purposes of thisinvention the only trigger action essential is one which permits full current to ilow suddenly in the controlled circuit when the controlling element reaches the critical potential, irrespective of whether the reverse action takes place or not. If the reverse trigger action does nottake place, as is the case with the '-I'hyratron, then as already described, the controlled circuit may be interrupted by using alternating or periodically interrupted direct current, in which event it interrupts itself when the potential of the control member recedes below the critical value. If a gas discharge device is used in which the reverse trigger action takes place, then obviously to interrupt the controlled circuit it is only necessary to return the control element to the critical value for shutting off the current in the controlled circuit, and uninterrupted direct current may be used in the controlled circuit. In summary, the system of the invention thus provides a pluralityv of gas discharge devices which, in non-operating positions, carry no current, and which have the grids thereof. respectively diiferently biased, so that the application of positive potential to the system will cause some or all of the grids to assume a potential which will permit current flow through the corresponding devices. Each of the devices hasy an associated relay adapted to operate contacts to open the anode circuits of -all of the devices which have less negatively biased grids. Accordingly, upon the application of a voltage pulse to the system one Lor more of the devices may start to carry current. However, the quick acting relay opens the anode circuit of all but one of the devices which tend to operate, and, accordingly, but a single one of the associated relays is energized. By this arrangement, it thus becomes possible to cause a single relay to close upon the application of a pulse of predetermined voltage, and to provide thereby for the selective operation of as many other relays as may bedesired. Thus, a given relay may be selected by the choice of the magnitude of the voltage pulse applied to the 'Amplifier combination The device of the invention may be combined with other devices for the production of other specialized results. 'In some instances, the permissible maximum voltage, which may be applied to a given line, is limited by the characteristics of the line, and the number of steps of voltage to provide for l,the desired number of different signals may be such that the difference in voltage between successive steps 'is less than that required by the system to distinguish accurately between the several signals to be sent. This invention, therefore, further includes the combination of the plurality of voltage pulse responsive devices, as above described, with an amplifier system adapted to increase proportionally the magnitude of the several voltage pulse signals. This arrangement is particularly shown in Fig. 2, in which there is disclosed a system similar to that of Fig. 1, including'the plurality of keys, gas discharge devices, the associated relays, potentiometers, and grid resistors with connections in general similar to those previously shown. Interposed between the line and the resistor I4 which replaces the line resistor LR of Fig. 1 there is, however, positioned an amplifying system A.

'I'he amplifier A may consist of a single amplier tube II, or may consist of a plurality of such tubes, according to the requirements of the system. The line .over which the signal current is to be transmitted is connected-to the grid of the tube I I, in parallel with the resistor I2, which corresponds to some extent, to the line resistor LR of Fig. 1, in-that it causes the application of voltage to the grid of the tube II when a key K at the sending point is closed. The' resistor I4 is connected in the anode circuit of the tube, and a bias battery C is connected in circuit with the amplifier tube grid.

' The system above described is essentially a resistance coupled amplifier system in which the resistors I2 and I4 correspond in general to the line resistor LR of Fig. 1, but the interposed vacuum tube causes an increase in the electrical magnitude of the voltage applied across the resistor Il. A direct coupled amplifier is desirable in systems in which random or low frequency pulses are to be amplified and is convenient for any frequency. However, in systems in which a rapid sequence of pulses is to be transmitted, as may occur with high speedtelegraphy, satisfactory results may be obtained by the use ofv an amplier in which the coupling between successive stages, the input line, and the voltage responsive devices, is obtained by inductive or transformer coupling, or by capacitive or condenser coupling. These latter forms of coupling, however, are useful only in the event that the signal pulse occurs at a relatively rapid rate, since such amplifiers do not normally function for the amplification of sustained steady values.

In this embodiment, the positive pulses delivered by the keys K, produce a voltage drop across the resistance I2. 'I'he bias battery C is desirably of such a voltage as to nearly block the tube II, allowing substantially no current to iiow therein, and in the resistance I4, in the absence of signals. Upon the arrival of the positive pulses from the keys K, the grid of the tube II is made less negative, allowing current to ow in the tubes II and the resistance l5, thereby delivering ampliied positive pulses to the potentiometer RR.

and the gas discharge device. These amplified voltage pulses then produce therein similar reaction to those described in connection with Fig. 1.

'I'he system above disclosed is particularly advantageous in connection with cable signaling devices, as is also shown in Fig. 2. In this embodiment, a similar form of sending system may be utilized to that-shown in Fig. 1 consisting of a plurality of keys K, and a similar potentiometer R, energized by a suitable source of curreni, as a. battery B. The variable voltage pulses are applied to the cable as shown, and conveyed therethrough to the amplier A, by which they are increased proportionately in electrical magnitude to a desired value and applied to the resistor Il, corresponding to the line resistor LR of Fig. 1. The voltage drop in the resistor I4 from the plate current in the tube I I changes the effective potential upon the potentiometer, RR, and one or more of the tubes T tend to vresistance coupled amplifier is desirable.

figure there is outlined a radio transmitting'systern adapted to transmit radio signals modulated in amplitude according to the relative voltage delivered thereto from the keys K, and a receiving set responsive to signals received from the sending set, adapted to deliver electrical pulses of differing magnitudes according to the amplitude of the received radio signals.

A plurality of keys K are provided as in the embodiment of Fig. l, and are associated with a potentiometer, R, which is energized by a power supply B, as before described. Closure of any one of the keys K delivers a voltage pulse of corresponding magnitude to the radio transmitting apparatus.

The transmitting apparatus, oscillating system,

high frequency oscillations by an amplifier of the type shown in Fig. 2, if the signal strength to be transmitted makes amplification desirable. Obviously the coupling between successive amplifying stages and between the amplifier and modulator circuit must be adapted to the type of pulse to be amplified. If these pulses are of low or random frequency, a direct coupled gi they occur at relatively rapid rates a capacitive or inductive type of coupling, as previously suggested, may be utilized. Also, the signal may be amplified at radio frequency after modulation. In any event, the system required is one which will convert voltage pulses of different magnitudes into radio frequency oscillations of corresponding'amplitude. I

The receiving member maybe of any convenient type of radio frequency receiver, which may include amplifier members for amplification at radio frequency, and an output detector or rectifier. The output device is'desirably associated with an output resistance corresponding to the line resistance LR of Fig. l, byf which a varying amplitude of high frequency signal applied to the detector device produces a proportionate unidirectional voltage pulse in the form of a voltage drop acrossthe output resistance. This voltage drop across the output resistance may be amplified, as shown in Fig. 2, or may be utilized directly for the operation of the selector device corresponding to that shown in Fig. l.

`By this embodiment of the invention, the desired signal originating as a voltage pulse may be converted. to a high ,frequency oscillation of corresponding amplitude, transmitted over a radio channel, received at a remote point, detected or rectified, reconverted to a corresponding voltage pulse and applied as a voltage pulse to the voltage responsive member of the invention to cause the selective operation of a predetermined gas discharge device and the predetermined operation of a single relay assembly for the production of a' predetermined signal, or a predetermined operation as previously described.

Telephone pulsing The system of this invention is conveniently applicable to the transmission of automatic telephone control signals. For this purpose a device may be provided at a subscribers station, or

at a telephone exchange, adapted to send single electrical pulses of a magnitude varying accord- 'I'he voltage pulse may be amplified before it is caused to modulate the may be vreceived at a central exchange or branch exchange and utilized to control the selection of the called subscriber. For this purpose a de'- vice similar to the receiving portion of Fig. 1 or Fig.'2 may be utilized with such changes as are necessary for the purpose, which will be indicated in the following description. This device may take any one of many forms, which will be obvious to those skilled in the art, its basic usefulness depending on the fact that it will close any selected one of ten or more line, or trunk selecting, circuits.

Referring to Fig. 4, the subscribers instrument may consist of the usual call bells 2l, condenser 22, induction coil 23, receiver 24, transmitter 25, and hook switch 23. These may be connected in any one of the usual ways, as, for instance, in the manner shown, which is very commonly used. In addition to the usual equipment there is also provided a plurality of push buttons 3l, 32, 33,

etc. Inthe drawings, for the sake of simplicity only five of these are shown to illustrate theprinciple. In practice any convenient number may be employed, as, for instance, ten, for opera- -tion in the decimal system of numbering. There is also provided an extra pair of contacts 21 and 28, on the hook switch adapted to close a circuit when the receiver' is raised.

Associated with. the push button is a resistance SR, tapped at as many points as there are push buttons, 2|, 22, 23, etc., the points preferably having equal resistances between them. This resistance should preferably be quite high in comparison to the line resistance. One end of this resistance is permanently grounded, as shown.

With none of the push buttons depressed, one Wire B of the subscriber's line goes directly to the receiver, transmitter, etc., while "the Vother wire G goes through contacts on each button connected in series, and, finally, also to the receiver, transmitter, etc.

It is to be noted that the wire B that goes directly to instrument is theone which is connected to the positive side of the common battery CB at the telephone exchange, and the system rcquires that the negative side of this battery be grounded. The other wire G is ultimately connected to ground at the exchange. l

When the receiver is lifted from the hook, the hook switch, through the springs 21 and 2B, completes a circuit from the battery side of thev line to the push buttons, as shown. This makes the push buttons inoperable unless the receiver is off the hook. When one of the buttons 2|, 22, 23,

etc., is depressed, the right hand springs connect the ungroundedf'end of the resistance SR to the battery side of the line, through springs 2l and 28. In this position the exchange battery, the battery side of the subscribers line, and the resistance SR, cooperate to form a simple potentiometer circuit, the resistance being bridged across the battery by having one of its terminals connected to the positive side of the battery through the line wire E, while its other terminal is connectedV to the negative side of the exchange battery through their common connection to ground. The left hand springs of the depressed button disconnect the line wire G from the instrument and connect it to oneof the taps of the ing to the digit to be indicated. These pulses is to be noted that the left hand springs of the push buttons are of thefhnalre before break" type, so that the operation of any push button does not break the linecircuit once it is established by removing the receiver from the hook. The necessity ior this will appear later.

The net result 'ci' the scheine ci? connections shown and described is that provides a conventional type of subscribers circuit when no button is pressed. `when the receiver is iiited oit the hoch and a button is pressed., the tele phone instrument proper is disconnected from the line, while the resistance associated with the push buttons is converted to a potentiometer', fed from the central cnice battery over one or" the line wires with ground return. The other line wire serves as the variable potential lead from the potentiometer and carries bach to the central oihce a potential depending upon the button pressed, within the limits ci the central otu tice battery. This part of the apparatus is, therefore, a counterpart of sending lteys, asz scciated potentlorneters, etc., shown in Figs. l., 2 and d, in other embodiments of the invention.

it the central cnice or sub-station, the two line wires pass through a chain ci contacts of the selector relays C) in the manner shown. The side of the line which feeds the potentiometer in the subscribers instrument then goes to the positive side of a source ci direct current, which may conveniently be the central office coinmon battery, the negative side of this battery (or other source) being grounded. The other line wire terminates at a resistance LR, the other terminal ci" which is grounded. This resistor is similar in iunction to the resistance LR of Figs. l and 2.

Connected to the saine terminal LR with the line wire is a potentiometer RR, which is the saine in function and purpose as the similarly lettered potentiometers of Figs. l and 2. it puts successively larger negative biases on the grids of the tubes Till, T32, T35, Tdt and Titti.

,it is to be noted that the number of tubes is one greater than the number of push buttons, and that the tube having the highest negative bias has alternating current supplied to its anode. y.all the rest oi the tubes are supplied with direct current anode power, which, for convenience, is shown as coming from the common battery CB ci theexchange. This anode supply oi direct 'current passes through malte contacts oi a relay Siti, placed in the G side of the subscribers line, the purpose of which will presently appear.

e relay til is shunted by a condenser to reduce the line impedance to voice currents.

The manner ci operation of the apparatus is as follows: when the receiver is lifted from the hook, a circuit is formed from the positive side of the battery CB, through the B side of the subscrlbers line. through the subscribers instrument, through the G side of the line, through LR and back to ground. This completes the circuit, since the negative side of CB is grounded. The resistance of LR. is so high that it constitutes by far the greatest part of the resistance of this entire circuit, hence, almost the full voltage of the battery CB appears as a. drop across LR. This ls sumclent to overcome the bias of the entire chain of tubes T, including T36, which has the highest bias in the chain. This permits current to flow through all the tubes and their associated relays N. which are quick acting and correspond to the quick acting 'relays N of Fig. 2. However. one set of contacts of the relay N36 interrupts the anode current for all the lower biased tubes in. the chain, as already described, and prevents the operation of all the relays N (except, of course, N35). The other set of contacts of N36 passes current through the slow acting relayv Ote, which corresponds to the relays O of 2. This relay now pulls up, connecting to the line the tone circuit. This tone circuit sends out over the line the well known dialing tone, indicating that the line is ready for use. in the event that this apparatus should be used in connection with an automatic line nder or selector switch of the type now in use, this feature would be particularly desirable, as it would cause the subscriber to wait until the line nder had operated, before operating a push button.

When the subscriber hears the ready tone, hepushes a button corresponding to the rst digit of the number he desires, for example, the button St. This disconnects the instrument from. the line and puts on the wire G a corresponding potential which is lower than that eX- isting when the instrument was across the line. This lower potential is insufi'icient to overcome the bias of tube Tilt. This tube, being supplied with alternating current therefore ceases to con duct. curr-ent at the next half cycle when the anode becomes negative. This causes the armature or relay Ns@ to drop back, the relay reconnecting the direct current to the anodes of the preceding tubes T. Y By the method already described, the relay corresponding to the button it now pulls up and permits the complete operation of its asso ciated slow acting relay 034i. The closing of relay @Sli connects the subscribers line to the corresponding selected line L36, Vwhich may be directly the line of the called subscriber, or which may merely lead to a group of lines or trunks from which further selection may be made by again pressing one of the buttons Si, 32, etc., accordingly, to the next digit of the number to be selected.

Since the tubes T (except T36) are supplied with direct current at `the anodes, the re-establishment of the negative bias on their grids does not interrupt the anode current; hence, the selected relay (Nitti in this case) remains energized after the corresponding button is restored to its normal position.

The operation of any of the relays O also connects to the-subscribers line the repeating coil, di, which, through its connection to the battery CB, furnishes the proper current to the line for energizing the called and calling subscribers instruments. This repeating coil need be connected to the contacts of the relays O, however, only if these relays are used to'select subscribers lines, that is, if they respond to the nal digit of the called number. If the relays O are used for intermediate digits, the coil 4| and the corresponding contacts of the relays O may be omitted. By this arrangement only one repeating coil will supply current to the line, and that coil will be connected at the selector relay of the last digit in the number. l

It will be noted that the anode current for the tubes T comes through a contact of the relay 30, which is connected in series in the' subscribers line, and so arranged that the tubes T are supplied with anode current only when the relay 30 is energized. It has also already been pointed out that the buttons 3|, 32, etc., have make-beforebreak contacts, hence, the pressing of any 'of these buttons does not even momentarily open the 2,oos,scs

linelr circuit, but merely changes the potential of the line wire G with respect to ground. The relay III, therefore, continues energized throughout lall the operation of the buttons, as long as the receiver is oil? the hook. When the conversation is completed and the receiver is restored to the hook, the relay 3U is de-energized, the supply of anode current to the tubes T (except T36) isv rent, to operate in series with the resistance LR.

Relays operable on very small currents are, however, commercially available, or the relay may conveniently be replaced by a suitable potential operated device, such as a vacuum discharge or gas discharge tube. As already explained, the line G is vat ground potential only when the receiver -is on the hook, and thereafter is continually at some potential higher than ground. The-grid of a triode may, therefore, be connected to the line wire G in place ofthe relay 30, and the change of potential thereon utilized to operate a relay in the anode circuit, this relay th'en performingl the function indicated as performed by relay l0.

It will also be apparent that in the above described embodiment, if each of the lines L3 I L32,

L33, etc., lead to another selector circuit, then, 4 if one ot the buttons 3|, 32 etc., is held down too.

long, it may also operate a selecting relay O in the next selector circuit, thereby causing an error.

".l'o obviate this, each successive selector circuit after the nrst may be provided with a device,

which will keep it disconnected from its corre-y -spoiiiding resistance LR., such as contacts on an appropriate relay, until Yafter the line wire G -ha's attained its highest potential, which occurs when none of the buttons are depressed and only the instrument is across the line. With -this arrangement the pressing oi a button once will then operate only one selector relay no matter how long the'button may be kept depressed. To operate the next selector-relay in the chain, corresponding to the next digit in the number, it will be necessary to let .each button come back to normal before pressing it, or another button, again. This action restoressthe khighest available" potential to line wire G, and permits the resistorA LR of the circuit last selected to be connected ,to that circuit. Means for,causing each successive selector circuit to remain disconnected from its resistance LR until Vafter the line wire Gf has attained a certain fixed potential, are readily available and will suggest themselves to those skilled in the art, and need not be here described.

The purpose of the foregoing description, relating to telephone signaling, has not been toshow a ilnished system of'automatic telephony, coml Y 1t viriiiaiso pe obvious to those skiiied in the art that alternate methods may be used other than those suggested, without departing from the spirit Vof the invention. As an example, the potentiometer at the subscribers instrument may be powered by a local battery, the vsystem may be used in a'local battery or magneto exchange, or it may be used with particular advantage over long distance lines, with or without a common battery at the exchange.

Thus, the system of the invention maybe used y to enable a subscriber, by suitable operations at his instrument, to select any one of a considerable number of lines leading to other exchanges or sub-exchanges, groups of lines, individual -lines, or selected means of ringing individual lines, and

to repeat this selection successively to `'effect the nal selection of a single line, and mea'nsof ringing any party on .that line, out of an entire telephone system.

` l Light responsive system The basic elements of ihe'invention described with Fig. 1 maybe utilized in combination with a photo-cell system for other useful functions.

- A photo-cell` is responsive to light, permitting a ilow of electrical current therethrough, which is vproportional to the illumination, a high illumination producing a larger current ow than a lesser illumination. When it is'desired to obtain responses in steps, depending upon the degree of illumination, thel embodiment of Fig. 5 may be utilized. As indicated, the photo-cell, which may be of the emission type, photo-galvanictype, or photo-resistor type,I is connected, as`shown,.to an ampliiier. As already explained in other embodiments of this invention, it is desirable that this ampliiier be'ofthe direct coupled type in order that it may faithfully amplify sustained current or voltage pulses, or pulses of random duration. Where the application is such that the pulses will be suiiiciently frequent and regular, then inductively and capacitively coupled ampliiiers may be used. Theoutput or this amplier is connected to the resistor LR, corresponding-to the lineresistor LR of Fig. y1. The gas discharge devicesof 'Fig.1 are provided, as indicated, by a box marked selector" shown in Fig.

5, and operated in a similar manner to close a circuit through the respective pairs of leads from the selector as indicated.

By this embodiment ofthe invention, agiven degree of illumination on the photo-cell causes a corresponding currentiiow therethrough, which is amplined and caused to `yield a suitable/poltage drop over the resistance LR, which, in turn, .causes the actuation of one of the gas discharge devices T, as shown in Fig. 1, and the actuation of the corresponding relay to close a circuit to the desired operabledeviee. A higher degree of illuminationV produces a higher current ilow through the resistor LR and closure of the lcorreshades, orlight reflecting, or transmitting power,

or color.4 Light from the sortable objects may be caused to impinge on the photo-cell, to cause the corresponding current ilow therein. This current flow produces a voltage drop-in theresistor LR, which causes the appropriate relay T to operate and close its contacts. Closure of contacts may thenbe used to produceany desired operation, such as the selection of sorting pockets.

This sorting operation may be conducted accord` ing to the reflecting power of the object, or according to its optical density, its light transmissive power or according to the presence,- or absence, or size of openings therein.

Alternatively, the device 'may be utilized ior the control of various members according to the intensity of illumination, such as the turning on and oi of successive steps of artiilcial illuminationpas the natural light in a given place varies, or such as the control of window shades, etc. It may be notedthat this device is one of the few available devices which are adapted to respond to vdeilnite discrete steps over the range of a continuous change of illumination, and that it responds in successive steps to the exciting energy changes..

- Remote control Manyother uses of the system of this invention will b e obvious, among which may be mentioned the use ofthe system in duplicate for remote control operation over a single line, of electrical switches at a sub-station or unattended generating station from a inain load dispatch center with automatic answer back, upon the occurrence of changes at the remote point, the controlof selected mechanical operations from a distance, such as the opening oi. selected chutes or outlets, etc., or the opening of valves in piping systems, the throwing of switches of various sorts and many other uses, which willoccur-to those skilled in the art.

The device of this invention thus- :provides simple means for the transmission of signals by single electrical pulses of differing electrical magnitude, primarily differing in voltage, but signincantly differing in current, since diiferingcurrents are readily convertedA into different voltages by the differing drops they produce alongv the resistances. The responses to these different voltages may be utilized independently for the control of a plurality of different predetermined pulses in which the significant 4factor is electrical magnitude rather than the -time duration, as is necessary for most signal impulses ofthe prior art.

Also since the general term gas discharge device has been used `heretofore to designate some electronic devices which do not possess the operating characteristics previously referred to, the term gas discharge device of the trigger action type", wherever it occurs in the claims appended hereto, shall be taken to mean. an electronic or gas discharge device having atcontrolled circuit responsive to a controlling element and having the operating characteristic that the controlled circuit passes substantially no current until the control element reaches a certain narrow predetermined range of electrical potentials and passes substantiallyl a predetermined current when the control element reaches-or'exceeds this range of potentials, further increases in the potential of the control element being substantially means for sending a plurality of signicant pulses of din'erent electrical magnitudes, and means selectively responsive thereto according to the electrical magnitude for the production of predetermined responses, said last mentioned means comprising gas discharge devices of the trigger action type.

2. An electricalsignaling system, comprising, in combination, means 'for sending electrical pulses of non-signicant timeduration and 'significant electrical magnitude, and means selectively responsive to the electrical magnitude of the signal, said last mentioned means comprising gas discharge devices of the trigger action type.

3. An electrical system comprising means for the production of electrical pulses of diiferent electrical magnitudes, means for the conveyance thereof toa remote point, and means selectively responsive to the electrical magnitude for the production of a predetermined response, said last mentioned means comprising gas discharge devices of the trigger action type.

4. In combination, a plurality of circuit mem- ,bers respectively adapted to apply diierent electrinected in parallel to said circuit respectively responsive to different applied voltages thereon, and means' actuated thereby for the production of a predetermined response and for preventing a response by devices actuable by lower voltages than the predetermined voltages.

5. lThe combination of a plurality oi' gas discharge devices of the trigger action type, means i'or normally `applying diierent biases to the grids thereof, means responsive to current ilow in `said devices, and means for varying the potential of the bias producing means for overcoming the grid biases of said devices.

6. In combination, a plurality of gas discharge devices of the trigger action type having grids, and anodes, means for applying diil'erent normal grid biases to the respective grids thereof, means for overcoming the gridf bias of said devices, and

, discharge devices of the trigger action type conmeans for causing only one thereof to pass curof a given indicating grid bias of a plurality of said devices, and means for preventing the response of the devices having lower grid biases.

8. Incombination, means for initiating a plu.- rality of electrical pulses of diil'ering magnitude, means for conveying such pulses to a remote point, a plurality oi' gas discharge devices of the trigger action type at the remote point respectively independently responsive to a predetermined signal pulse magnitude, and members actuated by the response of saidgas discharge devices.

9. In combination, a signal sending mechanism comprising a potentiometer and a plurality of associated keys, a signal conveying channel and a signal responsive member comprising a plurality of normally differently biased gas discharge devices of the ltrigger action type respectively responsive to different signal voltage magnitudes, means for preventing the operation of more than a single one of the group of gas discharge devices, and means for causing an operation in response to the operations of the selected gas discharge devices.

l0. In combination, means for initiating pulses of varying electrical magnitude, means for converting said pulses into oscillations of correspondingr amplitude, means for receiving said oscillations, means for detecting said oscilla- 'tions and producing voltages corresponding to varying the potential of said bias producing means with respect to the cathode of said gas discharge devices, said last mentioned means comprising a controllable voltage source.

12. In combination, a group of gas discharge devices of the trigger action type having grids, means for producing a plurality of normally different biasing voltages connected to said grids, relays associated with said gas discharge devices operable by -current flow therethrough, means for varying the potential of said bias producing members with respect to the cathodes of said gas discharge devices, said last mentioned means comprising a controllable voltage source, means for preventing the operation of more than one of the gas discharge'devices, and means operable by said discharge devices for producing a given response. y f

13. In combination, a plurality of gas discharge ,devices of the trigger action type, a member adapted to supply differing grid voltages to the several devices whereby the several devices are differently biased negatively, and means for supplying varying amounts of positive potentials to the biasing devices to convert the biases upon' some of the grids from negative to positive values.

14. In combination, a plurality of gas discharge devices of the trigger action type, a member adapted to supply differing gridvoltages to the several devices whereby the several devices lare normally differently biased negatively, means for supplying varying amounts of positive potentials to the biasing devices to convert the biases uponA some ofthe grids from negative to positive values whereby current is allowed to flow therein, relay means responsive to current flow in said tubes, and means-operable by said relay for producing suitable responses and preventing the flow of current through more than one gas discharge device.

15. In combination, means for producing signal pulses of varying magnitude, means for` amplifying the magnitude thereof, and means responsive in steps .to the amplied magnitude to produce' aresponse according to the magnitude of the original voltage pulses, said last mentioned means comprising gas discharge devices of the trigger action type. f

16. In combination, a photo-cell member responsive to changes in illumination, and a device ycomprising a-plurality of gas discharge devices of the trigger action type and respectively associated relays responsive individually in successive steps to the changes in illumination upon said photo-cell, said relays being adapted to be operated thereby for the production of other responses.

1'7. I n combination, means for initiating electrical pulses corresponding to intelligible characters, each character being represented by a single pulse of a differenty electrical magnitude from those representing other characters, means for conveying said pulses to a remote point, a system comprising a plurality of members respectively responsive to pulses of differing magnitudes, combined with means for preventing the operation of more than one device in response to a given pulse, and means actuated thereby for the recording of the various characters indicated by the pulses.

18. In combination, means for initiating electrical pulses corresponding to intelligible characters, each character `being represented by al single pulse of a different electrical magnitude from those representing other characters, means for conveying said pulses to a remote point, comprising a cable system and means for controlling the pulse form, a system comprising a plurality of members respectively responsive to pulses of differing magnitudes, combined with means for preventing the operation of more than one device in response to a given pulse, and means actuated thereby for the recording of the various characters indicated by the pulses.

19. In combination, means for initiating electrical pulses indicating by the electrical magnitude thereof the several numerical digits, means responsive thereto for determining the digit indicated comprising a plurality of gas discharge devices of the trigger action type and associated relays, and means actuated for selecting and connecting a predetermined numbered circuit.

20. An electrical signaling system, comprising, in combination, means for sending electrical pulses of non-significant time duration and significant electrical magnitudes, and means selectively responsive thereto, said last mentioned means including gas discharge devices of the trigger action type responsive to all the pulse values above a critical value differentfor each device and mechanism associated with each device for the production of a usable response and the prevention of response by a member having a lower critical value.

21. In combination, a plurality of gas discharge each of said devices, means for normallyapplyv ing diiferent grid biases to the respective'grids of said devices, means for overcoming the grid` bias of a group of said devices, and means for preventing the actuation of the iirst mentioned means of all the devices of said group except the -one most negatively biased.

22. In combination, a plurality of gas discharge devices ofy the trigger action type having grids,

means responsive to current now `in said devices,

means for normally applying different grid biases to the respective grids of said devices, means for overcoming the normal grid biases of a plurality of said devices, and means controlled by the passage of current through one of saiddevices for preventing the passage of current through the others.

23. In combination, a plurality of gas discharge devices of the trigger action typehaving grids, individual means controlled by current now in each of said devices, means foinl normally applying different negative grid biases to the respective grids of said devices, means for overcoming the negative grid biases of a group of said devices, l and means controlled by the passage of current through the device of highest negative grid bias which has been overcome for preventing the passage of current through the devices of lower grid bias.

24. In combination, a plurality of gasdischarge devices ofthe trigger action type having grids, means responsive to current flow in the plate circuit of said devices, means for normally applying dlil'erent negative grid bias to the respective grids' of said devices, means for overcomingthe negative grid bias of a plurality of saidA devices, and means controlled by the current flow in the device of highest negative grid bias overcome for opening the plate circuit of the devices having lower grid biases.

25. In combination, a plurality of gas discharge devices of the trigger action type having grids, slow acting relays for producing a, desired response controlled by current ilow in the plate circuits of said devices, means for applying different negative grid bias to the respective grids of said devices, means for overcoming the negative grid bias of a plurality of said devices, 'and fast acting relays controlled by current non in the plate circuits of said devices for opening the plate circuits of the devices having lower grid biases.

26. In combination, means for initiating electrical pulses correspondingto intelligible characters, each character being represented by a single pulse of different electrical magnitude from those representing other characters, means for conveying said pulses to a remote point, said last mentioned means comprising a cable system and means .for controlling the pulse form, a system comprising a plurality of gas discharge devices of the trigger action type respectively responsive to pulses of different magnitude combined with means for preventing the operation of more than one device in response to a given pulse. and means actuated: thereby for indicating the various characters indicated by the pulses.

MAURICE D. SARBEY.

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