US2350193A - Auxiliary telephone apparatus - Google Patents

Description

May 30, 1944. c. s. RHoADs AUXILIARY TELEPHONE APPARATUS Filed Aug. 21, 1945 2 Sheets-Sheet 1 Swim@ I mm N IWI @@W @E I I L QN NSS@ N INVENTOR C. S. Rhoads BY u. 'ATTORNEY N III-III' I May 30, l1944. c s, RHoADs v2,350,193

AUXILIARY TELEPHONE APPARATUS Fi-led Aug. 21, 194s 2 sheets-sheet 2 ljlllIi-Hh N IIHIr INVENTOR C. SJZkoLs A TTORNE Y Patented May 30, 1944 UNITED STATES PATENT OFFICE AUXILIARY TELEPHONE APPARATUS -Charles Stanley Rhoads, Albany, N. Y., assigner.

to American Telephone and Telegraph Company, a corporation `of Newl York Application august 21, 194,3, serial No. 499.494

(Cl. 17a-4 3);

14 Claims.

This `invention, relates to telephone systems. More particularly, this invention relates to apparatus for signaling between two or more telephone offices over the trunk or other lines interconnecting said oices. Still more particularly, this invention relates to auxiliary or emergency equipment for use at telephone offices to provide facilities for signaling between two olces which are separated from each other by one or more intermediate` ollces.

lt has heretofore been proposed to provide emergency telephone equipment suitable for sig.- naling between a community dialr officewhich usually is unattended and has automatic switching machinery for its subscribers. to dial each other-and a master or operator officewhich usually is located near a city and is attended by an operator and includes facilities to connect telephone subscribers in the community dial ofce area to subscribers in the master office area and elsewhere over the trunk circuits extending between the two offices. An arrangement in which the emergency telephone equipment is permanently connected to the trunk conductors and yet does not interfere with normal signaling and conversation over the trunk conductors is disclosed in my copending application Serial No. 483,983, filed April 22, 1943.

However, it often happens that the community dial oiiice is connected tothe master or operator cnice by one or more intermediate or tandem oces which may also be unattended and that the emergency equipment must be used to signal from the community dial oice to the operator at the master or operator oice through the tandem or intermediate oices Whenever desired. The present invention is intended to provide simple and inexpensive equipment for this purpose that will operate unfailinglyat all times. The invention will include apparatus not alone for connecting the community dial oice to the master oiiice through the intermediate or tandem oice but also for simultaneously disconnecting the trunk equipment atl the intermediate ortandem oiice or offices.

This invention will be better understood from the more detailed description hereinafter following, when read in connection with the accompany-ing drawings in which Figure 1 shows the invention applied to a telephone system includ-` ing a master oiice and a community dial' cnice which are connected to each other through an intermediate or tandem ofce, and Fig. 2 shows generally a modification of the arrenecment'of liig'` 1.

Referring to Fie,- 1. of. the. drawings, a com.- munity dial oiice CDO is connected through a tandem oiiicc TDO to.. a master or operator office.. MO.v The community dial oiiice CDO. is connected to the tandem oiiice TDO by a loop dialing trunk I Ki` which includes conductors T1 and R1- The tandem office 'I DO is. connected. to the master office MQ by another loop dialing trunk TKz which includes coriductors T2. and Rz. Qne of a plurality of subscribers lines in the area of the community dial oiiice CDO may include conductors L; and La, and telephone calls may be transmitted in both directions in a wellknown manner between the subscribers, line such as, L1-L2 over the trunks TK1 and to the office. MOv and to any subscriber in the area o f the master oce or elsewhere. Any subscribcrs. line such as Li-Lz in the community dial oice area, may gain access to trunk TKji (or to` any other ,suchl trunk) merely by dialing O.-, for example.. whereupon the subscribers line will be connected to a trunk such as TK1. The regular officer equipment at the three offices, so far as it may relate to this invention, is shown for illustrative purposes, together with additional equipment different from. that heretofore used. at these oices, which is suitabla in accordance with this. invention to provide auxiliary ,Sien aling apparatus for use, `for example, in emergencies. f

The regular equipment oi the twoofiices will now be only briefly described. The windings of the relay Wi at the COmmunty dial ofce CDO and the windings` of the relay P2 at the tandem office TDO are connected in a series circuit which includes battery,` the upper winding of relay W1, the upper secondary Winding of thc rcpcatine coil RLi, the upper armature. and back contact of. the relay U1, thc conductor T1 ci trunkl TK1, the upper primary winding of A a repeating coil such as HL2, the windings of, the polarized relay Pz, the lower primary winding of the repeatingv coil RLz, the conductor Ri of; trunk TKi, the lower armature and' backcontact of relay U1, the lower. secondary Winding ci. the. repeating coil RL1, the lower windingV ofl relay W1, and ground4 The current that traverses thc windings of relays Wi and P2 will not operate these relays but they may be operated, as will be described hereinafter, whenever a call is made from, for example, the. subscriber having the line L1-L2 connected to the community dial oiiicc CDO. toa subscriber connected to the master office MO. A, similar circuit interconnects the windings, of relay Wi at the. tandem oicc 'ICDQ make contact of relay S1.

ing the line L1-L2, forV example, connected to the community dial o-ice CDO, to a subscriber in `the area of the master office MO, then in response to a predetermined dialed numberfbattery will be connected to the subscribers circuit Li-hz,y causing relay S1 to operate. The operation of the relay S1 will cause relay U1 to operate over an obvious circuit completed by the armature and When 'relay 'U1' 'operates, its armatures will reverse' the .direction of current flow to the windings.' of relay -Wi and the windings of relay P2. This reversal of curirent is brought about by the upper armature of relay U1 which connects the conductor T1 of trunk TK1 to the lower secondary winding of re-A likewise reverse the direction vof current flow through the windings of relay W2 at the tandem oce TDO and through the windings of polarized relay P3 at the master office MO, thereby also causing the relay P3' to become operated. Upon the'operation of relay P3 a lamp LPr will be lighted to attract the attention of the operator at the master oice MO. Both relays P2 and P3 are or the polarized type and, before relays U1 and U2 operate, the armatures of the respective relays P2 and P3 are retained againsttheir back stops. The relays P1 and P2 will operate only when the currents therethrough are reversed by relays U1 and U2 respectively. It is to be noted that the trunk equipment at the tandem point TDO will connect the trunk TK1 to a trunk such as TK2 automatically after the subscriber having the line L17-L2 has dialed O and been connected to trunk-TKi. The relay U2 of the selected trunk will be operated because the polarized relay P2 has operated.

In response to the visual signal given to the operator by the lamp LP1, the operator at the master office MO may answer the call -by inserting the plug PL of her answering cord into the jack lJK1 in the usual-way. This will con-i nect battery to the tip and ring terminals of the jack JK1 to establish a flow of current through the secondary windings of the repeating coil RLc and through the winding of relay V, thereby operating relay V. Relay V will close a circuit in shunt with the right-hand portion of the windings of the polarized relay Pa, thereby substantially reducing the resistance in the circuit ofv'the windings of relay P3. This reduction in the resistance will allow a greater current to flow through the windings of relay P3 and cause other apparatus (not shown) to be operated to control coin collector apparatus and to control other circuits. v

Suppose that in an emergency a repairman or other rauthorized person who is at the community dial o-ce CDO or who has been dispatched to that oiiice, upon arriving at the otce iinds the regular equipment out of order and he is therefore unable to use the regular equipment to com'- 75 municate with the operator at the master cnice MO. He may then use the auxiliary equipment provided by this invention to signal and converse with the operator at the master oirlce MO.

To signal the operator at the master ofce it is necessary to use the magneto generator MG1 of the magneto set M51 at the community dial office CDO in the usual wayby operatingthe magneto or hand generator. MG1 while the'receiver of the magneto set MS1 is retained on its switchhook. The gas tubes G1 and Gz-Which may be of the 333A type and are otherwise known as cold cathode tubes-will both be flashed simultaneously. The circuit for ionizing the gas tube G1 includes the hand generator MG1, the two cathodes of the tube G1 (otherwise known as the control gap of the tube and shown here by two parallel lines) and the resistance of the tube and ground. The circuit of the tube G2 at the tandem cnice TDO includes the hand generator MG1, the conductor R1 of trunk TK1, conductor II, the right armature and back contact of relay H, the cathodes or control gap of tube G2, and the resista-nce 'of the tube and ground. As the tube G2 becomes ionized, relay C becomes operated, the operating circuit including the generator MG1, conductor R1, conductor II, the right armature and back contact of relay H, the lower cathode and anode of tube G2 (otherwise known as the main gap of the tube), the winding of relay C and ground. The winding of relay C will receive from generator MG1 only that portion of the generated current that iiows in a positive direction from the anode to the lower cathode of tube G2. Thearmature of relay C will therefore vibrate between its contacts ata rate corresponding tothe frequency of the hand generator MG1, which may be, for example, 20 cycles per second. Each closure of the make contact of relay C will cause:

' tube G3 at the master oilce MO to vbecome ionized, the ionizing circuit including batteries B1-B2, the armature and make contact of relay C, conductor I2, conductor R2 of trunk TK2, conductor I3, the upper right swinger of key K and its contact, the lower right swinger of key K and its contact, the cathodes (or control gap) of tube G3 and its resistance to-ground. As the tube G3 becomes ionized, the relay E-which may be a drop of any well-known type-will become operated, the operating circuit including batteries B1--B2, the armature and make contact of relay C, conductors I2, R2 and I3, the upper and lower right swingers of key K and their contacts, the left cathode and anode (or main gap) of tube Ge, the winding of relay E and ground. The operation of relay E will cause the lamp LP2 to be lighted by the completion of an obvious circuit established by the armature and make contact of relay E. The illuminated lamp LP2 will signal the operator at the master oiice MO that she is wanted on the emergency circuit.

The operator at the master oiice may answer the call made over the emergency or auxiliary circuit by inserting the plug PL of her answering cord into the additional jack JK2. To complete the talking path to the calling party the operator will operate the key K to its upper position and the key K will be locked in that position. By so operating key K, the gas Within tube G4 at the tandem oil'ice TDO will become ionized, the ionizing circuit including battery Ba-Bi, the left upper swinger of key K and its contact, conductor I3, conductorR2 of trunk TX2, conductor l2, the armature and back contact of relay C, the cathodes (or control gap) ofl tube G4 and its resistor to ground. As soon as tube G4 is so ionized,the

relay H will become operated, the operating-,circuit including batteries Bs-B4, the upper left swinger of key K and its contact, conductors I3, R2 and I2, the armature and vback contact of relay C, the right cathode and anode (or main gap) of tube G4, the winding of relay H and ground. The operation of relay H will complete a circuit to the winding of relay J, the circuit including battery V5, the winding of relay J, the thermistor TH, the inner left armature and make contact of relay H and ground. The thermistorTH is inserted in series with the winding of relay J to allow the relay J to become operated only if the battery B5 supplies current thereto for a predetermined interval of time, such, for example, as 6 seconds. Such an interval of time will normally elapse upon the closure of the key K to its upper or talking position. Thus relay J will become operated in response to the movement of the key K to its talking position.

It is noted that relay J is employed for the purpose of connecting the trunk IKg to the trunk TK1 at the tandem oflice TDG, the interconnected circuit including the two armatures of relay J and their make contacts together with oondensers C1 and C2, respectively. Thus the master cmce MO and the community dial cnice CDO are connected to each other through the tandem office TDO by equipment including relai7 J controlled by the operator at the master oice MO. The outer left armature and make Contact of relay Hare employed to provide a shunt path around the anode and right Cathode (or main gap) of tube G4 to extinguish the tube G4 immediately after the relay H operates. This will preserve the tube G4 against destruction and increase its active life. Moreover, the winding of relay H Wiil be connected to batteries 13s-B4 through the icy-pass circuit provided by the cuter left armature and make contact of relay H and the armature and back contact of relay C.

It has been shown that upon the operation of the hand generator MG1 a signal is transmitted to the master office operator to attract her attention and that the master oice operator may control the connection of the trunks between the various offices to enable her to converse with the calling party. The conversation will take place over the circuit of jack JKz, trunk M2, the two armatures of relay J and their make contacts, condensers C1 and C2, trunk TKi and the magneto set MS1 at the community dial office CDO. After the conversation is completed the operator will restore the key K to its normal position. This will release both relay H and relay J at the tandem cnice TDO and return the equipment at that oilice to its normal condition.

Should the operator at the master office MO desire to recall the calling party at the community dial oce CDO, she may operate her key K to its lower or ringing position which will close the key K only for a brief interval of time. When key K is thus operated to its lower or ringing positicn, the tube G4 at the tandem oice TDO will be flashed over a circuit which includes the ringing generator RG, the lower left swinger of key K and its contact, conductor I3, conductor R2 of trunk TKg, conductor I2, the cathodes and resistance of tube G4 and ground. Whenever the gas of tube G4 becomes ionized, relay H will operate for a brief interval over a circuit similar to vthat just described except that the winding ci relay H is substituted for the left cathode and resistor of the tube G4. The relay J will remain unoperated, however, because the now of current from battery B5 through its winding and through the thermistor TH will be insufficient in duration to cause the relay to become operated.' Whenever the instantaneous value of the ringing generator RG voltage recedes below a predetermined value, tube G4 will be extinguished and relay H will be released. Relay H will therefore be repeatedly-operated at a frequency corresponding to the frequency of the current rof ringingy generator RG. This frequency may be, for example, 20 cycles perseconcl.

Each closure of the make contact of the righ armature of relay H in response to the operation of relay H will connect batteries B1-B2 to the cathodes of tube G1 over a circuit which includes batteries B1-Bz, the rightv armature and make Contact of relay H, conductor ii., conductor R1 of trunk TK1, the cathodes (or control gap) of tube G1 and its resistor and gro-und. The tube G1 will therefore becomes ionized upon each operation of relay H. But, as already noted, relay H will release at regular intervals. 'Upon each release of relay H the batteries B1-,B2 will be disconnected from the tube G1. The tube G1 will therefore become ionized and deionized-at the frequency of generator RG. And so on.

As the tube G1 becomes ionized, the biased ringer of the magneto set MS1 at the oiiice CDO will receive a pulse of current from batteries B1-B2 over the circuit just described for the ionization of tube G1 except that the ringer Will be substituted for the lower cathode and resistor of tube G1. In other words, the biased ringer of the magneto set M51 will be operated by'properly poled pulses of current produced by the vibration of the right armature of relay H which reach the ringer through the main gap of tube G1. The current through the ringer will bel interrupted upon each deionization of gas of tube G1. Thus the ringer will be repeatedly operated according to the ionization and deionization of the gas of tube G1 and this will attract the attention of the party that previously made the call to the master office operator. After so signaling the calling party the operator may again move the key K to its upward or talking position to complete the talking path to again "converse with the calling party.

It has been shown that the operator may recall the calling party by ringing over the conductors of the trunks between the various offices without connecting the trunks to each other. The trunks are connected to each other only when the operator is to converse with the calling party and this occurs only upon the operation of the relay J at the tandem ofce TDO' in response to the operation of key K to its upper or talking position in which position the key K remains locked.

It is observed that the ringer of the magneto set M531 is operated in response to pulses of current transmitted through the gas tube G1. The ringer does not receive the actual ringing current of the ringing generator RG but it merely receives pulses derived from the ringing generator RG by the equipment including relay H, as already explained hereinabove. The ringer is biased so as to respond to the polarized pulses derived from the ringing current.

An authorized party may also use the magneto generator MGz at the tandem oliice TDO to similarly signal the operator at the master oilce. By operating the hand generator MGz, the hand generator circuit is completed andthe generated current is supplied over the conductor I2, conductor'Rz of trunk TKZ, conductor I3 and through the right contacts of key K to the tube Ge to flash the tube G3 in a manner similar to that already described hereinabove. This will again operate relay E at regular intervals and light the lamp LP2 to attract the operators attention. The operator may then converse with the calling party at the tandem office TDO by operating the key K to its upper or talking position or, if desired, she may call the party at the tandem oice TDO by operating the key K to its lower or ringing position. The circuits completed by the manipulation of key K to signal the magneto set MS2 at the tandem oiflce TDO are similar to those already referred to hereinabove and therefore need not be further described.

Fig. 2 illustrates a modification of the arrangement of Fig, l, excluding, however, the trunk and other equipment not required to an understanding of the features of the Fig. 2 modification. When an authorized party operates the magneto generator MG1 at the community dial oice CDO, the gas tube Gs at the tandem oice TDO will become ionized, the interconnected circuit for ionizing the gas of tube G1; including the hand generator MG1, conductor R1 of trunk TK1, conductor 2|, the cathodes (or control gap) of tube G6 and the resistor of that ytube and ground. As soon as tube G becomes ionized, tube Gs at the master office MO will also become ionized, the interconnected circuit for ionizing the tube Gs including the resistor, the lower cathode and anode of tube G5, conductor 22, conductor R2 of trunk TKz, conductor 23, the swinger and normal contact of key K1, the cathodes (or control gap) of tube Gs, and the resistor of the tube and ground. Upon the ionization of the gas of tube G6, the relay E1 will become operated, the operating circuit including battery B1, the winding of relay E1, the anode, lower cathode and resistor of tube Gs and ground. Upon the operation of relay E1 the lamp LPz will become illuminated by the completion of an obvious circuit controlled by the armature of relay E1, and this lamp will signify to the operator at the master oiiice MO that she is wanted to answer a call on the emergency or auxiliary circuit.

It will be observed that the voltage generated by the hand generator MG1 is not only suicient to ionize the gas Within the tube G5 but at the same time produces a voltage at the anode of tube G5 of sufficient magnitude to ionize the gas of the tube Ge. This arrangement of tandemconnected tubes has been tried and found to operate satisfactorily. However, if additional voltage is required to insure the operation of the gas within tube Ge under special conditions (such as, Where the interconnected circuits include very large impedances), a properly pcled battery may -be inserted in series with the anode of the tube G5. That is, a battery may be inserted in the conductor connecting the anode of tube G5 and the terminal to the upper cathode of tube G7 and poled so that the positive terminal of the battery is adjacent to the anode of tube G5. As already explained, this additional source of voltage is not required except in unusual circumstances.

A relay J1 is employed as in Fig. 1 to connect the trunk TK1 to the trunk TK1 under the control of the key K1 at the master oiiice MO. Re-

lay J1 is shown' with its winding connected to the anode of the tube G1 but this relay will remain unoperated in response to the voltage produced by the hand generator MG1. The relay J1 will become operated only uponthe operation of the key K1 at Ithe master oiiice as will now be described.

In response to the illumination of lamp LP2 at the master ofiice MO, the operator may insert the plug of her answering cord into the jack JK2 to converse with the calling party at the community dialV office CDO. To complete the connection the operator will operate key K1 and thereby ionize the gas of the tube Gv at the tandem ofce TDO, The operating circuit for the tube G7 includes batteries B11-B9, the swinger and upper contact of key K1 (which is a key of the locking type), conductor 23, conductor R2 of trunk TKz, conductor 22, the cathodes and resistor of tube G7 and ground. As tube G7 becomes ionized, relay J1 will become operated, the operating circuit including batteries Biz-B9, the upper contact and swinger of key K1, conductors 23, R2 and 22, the upper cathode and anode (or main gap) of tube G7, the Winding of relay J1 and ground. In response to the operation of relay J1 the tip and ring conductors T2 and R2 of trunk TK1 will become connected to the tip and ring conductors T1 and R1 oi trunk TK1, through the upper and lower armatures of relay J1 and their make contacts and condensers C1 and C2, respectively. This will complete the talking path between the jack JKz at the master oce MO, and the magneto set MS1 at the community dial oice CDO through the tandem ofce TDO. Upon the completion of the conversation the key K1 may be returned to its normal position to release relay J1 and to return all the equipment to its normal condition. As in the case of the arrangement of Fig. l, the operation of relay J1 is employed not alone to connect the two trunks TK1 and TKz to each other at the oflice 'I'DO whenever desired by the operator, but also to remove all the trunk equipment from the interconnected talking path at the oce TDO.

In the arrangements of both Figs. l and 2 a relay, such as E1 of Fig. 2, has been employed to control the illumination of the lamp LP2 to signal the master office operator. If desired, a ringer may be used in place of the relay and lamp. The ringer may, for example, be connected between the anode of tube G6 and ground and it should be biased to respond to the pulses traversing the 'anode circuit (or main gap) of tube Gs in response to the operation of the hand generator MG1 at the community dial oice CDO. The ringer may, for example, be connected berate which corresponds to the frequency of the current produced :by the generator MG1. The lamp LPz at the master oice MO heats slowly and hence will be illuminated in response to each operation of the hand generator.

The arrangement of Fig. 2 illustrates a modied scheme for establishing a talking path through a tandem or intermediate office. Although it does not illustrate additional equipment for recalling the calling party whenever desired, equipment for signaling the calling party is set forth in Fig, 1 and may be added to the arrangements of Fig. 2 if so desired.

4Although the arrangements of both Figs. 1 and 2 illustrate a community dial oilice CDO connected to a master office MO through but one intermediate or tandem office TDO, it is clear that the arrangement is readily applicable for interconnecting the two oices CDO and MO through any desired number of intermediate or tandem offices such as TDO. To' accomplish this it is simply necessary'to insert equipment similar to that at the oiiice TDD at each of the other intermediate oices. In this case, however, it may be necessary to insert additional sources of potential inseries with the anode of the tube G at each intermediate or tandem oiiice, as already noted hereinabove.

While this invention has been shown and described incertain particular .embodiments merely for the purpose of illustration, it will b-e understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

l. The combination of a ringing generato-r, two three-element gas tubes, each having two cathodes and an anode, the generator being connected to the cathodes of one of said tubes, the anode and one of the cathodes of which are com nected to the cathodes oi the other of said tubes, an indicating device, and a relay connected to the anode and one of the cathodes of said other tube, said'indicating device being controlled by said relay.

2. The combination of a source of alternating current, first and second gas tubes each comprising two cathodes and an anode, means for connecting said source to the cathodes of said rst tube, the cathodes of the said second tube being connected to the anode and one of the cathodes of said first tube, indicating means, and means connected between the anode and one of the cathodes of said second tube to operate said indicating means.

3. Signaling apparatus comprising a source of ringing current, first and second gas tubes each including two cathodes and an anode, means for connecting said source to the cathodes of said iirst tube, means for connecting the anode and one of the cathodes of said rst tube to the cathodes of the second tube, an indicating device, and means connected to the anode and one of the cathodes of the second tube to operate said indicating device.

4. Signaling apparatus comprising a source of alternating current of predetermined frequency, an indicating device which is selectively responsive to current of said predetermined frequency, first and second gas tubes each including two cathodes and an anode, means for connecting said source to the cathodes of said rst tube, means for connecting the anode and one of the cathodes of said iirst tube to the cathodes of said second tube, and means connected to the anode and one of the cathodes of said second tube to operate said indicating device.

5. Signaling apparatus comprising a source of alternating voltage of predetermined frequency, an indicating device selectively responsive to pulses of current of said predetermined freouency, irst and second gas tubes each. including two cathodes and an anode, means for connecting said source ci alternating voltage to the cathodes of said iirst tube, a source of unidirectional voltage, a relay having its winding `connected between the anode and one of the cathodes of said rst tube, means controlled by said relay for connecting said source of unidirectional voltage in series with the cathodes of said second tube. and means connected to the anode and one of the cathodes of said second tube to operate said indi-- eating device.

6. The combination of a source of alternating voltage, a source of direct voltage, a gas tube having two cathodes and an anode, means for connecting either of said sources to the cathodes of said tube to ionize the gas within said tube, a rst relay having its winding connected between the anode and one of the cathodes of said tube, a second relay, and a thermlistor connected in series with the winding of said second relay, said secondrelay being controlled by the armature of said iirst relay. 1

7. The combination of a gas tube having two cathodes and ari-anode, means for applyingalternating voltage between said cathodesvto periodically ionize the gas within saidy tube, means for applyingv unidirectional voltage between said cathodes to continuously ionize the gas within said tube, a translating device connected between the anode and cathode of said tube and responsive to the ionization of the gas within said tube, a relay, a thermistor connected in series with the winding of said relay in a circuit controlled by said translating device, said relay being operated only when the gas within said tube is continuously ionized.

8. The combination of a gas tube having two cathodes and an anode, the gas within said tube being periodically ionized upon the application of alternating voltage to said cathodes and continuously ionized upon the application of unidirectional voltage to said cathodes, a relay, and means interconnecting said relay with the anode of said tube for operating said relay when the gas within said tube is continuously ionized and for preventing the operation of said relay when the gas is periodically ionized.

9. The combination of a gas tube which is continuously ionized in response to unidirectional voltage and periodically ionized in response to alternating voltage, a relay, means responsive to the continuous ionization of said tube to operate said relay, and means to prevent the operation of said relay when said tube is periodically ionized.

10. The combination of a gas tube which is continuously ionized in response to unidirectional voltage and periodically ionized in response to alternating voltage, a relay, an indicating device, means responsive to the continuous ionization of said tube to operate said relay and to prevent the operation of said indicating device, and means responsive to the periodic ionization of the gas within said tube to operate said indicating device and to prevent the operation of said relay.

11. The combination of a gas tube which is continuously ionized in response to unidirectional voltage and periodically ionized in response to alternating voltage, a translating device, a frequency selective device, means responsive to the continuous ionization of the gas within said tube to operate said translating device, and means responsive to the periodic ionization of the gas within said tube at a predetermined frequency to operate said frequency selective device.

l2. A claim according to claim 11, with the addition of means to prevent theoperation of said translating device when the gas within said tube is periodically ionized.

13. The combination of two lines, a relay for controlling the connection between said lines, a gas tube which is continuously ionized in response to unidirectional voltage and is periodically ion- :ized in response to alternating voltage, a ringer, means responsive to the continuous ionization of said tube to operate said relay to connect said said tandem ofce and said community dial office respectively, each gas tube having two oathodes and an anode, means for transmitting alternating voltage from said master to said tandem omce to ionize the .gas between the cathodes of said rst tube, means responsive to the ionization of the gas of said rst tube to transmit a unidirectional Voltage from said tandem oce to said community dial omce to'ionize the gas between the cathodes of said second tube, an indieating device at said community dial omce ccnnected to the anode and one of the cathodes of said second tube and responsive to the ionization of the gas within said second tube, a, relay at said tandem oice connected to the anode of said rst tube for controlling the connection between said Iirst and second trunks, a thermistor connected in series with the Winding of said relay, and means for transmitting unidirectional voltage from said master olce to said tandem oce to ionize the gas between the cathodes of said rst tube and for operating said relay.

CHARLES STANLEY RHOADS.

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