US2413001A

US2413001A - Communication system

Info

Publication number: US2413001A
Application number: US552418A
Authority: US
Inventors: Harry H Schneckloth
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1944-09-02
Filing date: 1944-09-02
Publication date: 1946-12-24
Anticipated expiration: 1963-12-24

Description

De@ 24, 1946- H. H. scHNECKLoTl-l 2,413,001

COMMUNICATION SYSTEM Filed Sept. 2, 1944 3 Sheets-Skiset 1 /NVEN ro@ H. H. SCH/VECKLOTH ATTORNEY H; H. scHNEcKLcTl-l 2,413,001

COMMUNICATION SYSTEM Filed sept. 2, 1944 s sheets-sneeze,

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POLAR/Z50 ATTORNEY l s sheets-'sheet s H. H. SCHNECKLOTH COMMUNICATION SYSTEvM Filed Sept. 2, 1944 Dec. 24, 1946.

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Patented Dec. 24, 11946s COMMUNICATION SYSTEM Harry H. Schneckloth, Forest Hills, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application September 2, 1944, Serial No. 552,418

22 claims. l

This invention relates to telephone systems and particularly to systems comprising a master ofiice and one or more unattended automatic oiices.

It is the object cf the invention to improve the arrangements for transmitting alarm signals from unattended automatic oflices to a master office.

It is usual to provide alarm apparatus in an unattended dial cnice which is effective when a trouble condition exists to seize a trunk to a master ofce and upon answer of the call by an operator in the master officevto transmit a tone signal to indicate that the call is a trouble alarm call from 'the unattended oice. It is also known to provide a trouble checking line in the unattended ofce with which connection may be established on a call from an operato;` or maintenance test man in the master oflice to determine whether any trouble exists, and the character of the trouble, in the unattended oice.

This invention is an improved alarm arrangement in a system comprising an attended master office and a plurality of unattended dial oiiices whereby on a trouble checking call initiated by an operator in the master office to any one of the unattended dial oices, signals are transmitted from the unattended office to operate a visual signal apparatus in the master office indicating that no trouble exists in the dial office or indicating the character of the trouble which does exist n the dial oflice, there being a set of such signals in the master omce for each dial office from which alarm signals are received.

A feature cf the invention is the provision of signal transmitting apparatus in an unattended dial oflice for transmitting to a master oflice voice frequency signals of different frequencies. One frequency is used to indicate that no trouble exists in the dial office, and each of the other frequencies indicates a different kind of trouble in the office.

Another feature of the invention is the provision of signal receiving means in the master ofce for receiving voice frequency signals of dif- -Y ferent frequencies for the different alarm condiv tions which may exist in a connected dial office and for indicating that no trouble exists in the dial ofce if such is the case.

Another feature of the invention is the provision in an attended oice of signal means for indicating whether or not any trouble exists in an unattended automatic oflice, the operation of the signal means being maintained for a predetermined length of time after its operation, thereby tion to the specific arrangement and system 1 shown but is generally applicable to alarm signaling systems between attended and unattended oices.

Referring to the drawings:

Fig. l shows the alarm signaling apparatus AL in a master oice;

Fig. 2 shows an operators position comprising the cord CDI, a trunk circuit TCH associated with a trunk TI extending to one unattended dial office, and a trunk circuit TG2 l associated with a trunk extending to another unattended dial office; and

Fig. 3 shows, in an unattended dial office, a trunk circuit TCI2, an incoming selector ISI associated with the trunk circuit TCI2, a connector Cl and alarm apparatus ALI. Fig. 3 also shows a subscribers station A, line LI and line circuit LCI, a line nder LFI and a first selector SI for use in establishing connections on calls originating in the dial ofce.

The subscriber stations in the unattended dial oflices are of the type provided on lines terminating in common battery central offices and each includes a dial or other impulse sender for controlling the operation of automatic switches through which desired connections are established. The line circuit LCI which comprises a line and a cut-oil relay connects the line Ll to terminals in the banks of line finders for originating traffic and to terminals in the banks of connector switches similar to the connector CI for terminating traiiic. The line finder, selector and connector switches may be of the well-known two-motion step-by-step type. Reference may be had to Automatic Telephony by Smith and Campbell, 2d Edition, pages 53 to 65 for a description of the structure of such switches and their operation when used as selectors and connectors. Reference may be had to the patent to R. L. Sto-kely, No. 1,799,654, April 7, 1931, for a description of the operation of a step-by-step line finder. Each of the switches LFI, SI, ISI and CI is represented in the drawings by a set of brushes and a single set of terminals, all omitted apparatus being represented by the broken lines connected t the brushes.

The alarm equipment ALI comprises a line relay connected to the tip and ring terminals of the terminal set I 5i! in the banks of a group of connectors including the connector CI, a transformer |52, alarm relays |62, |63 and |54 and sources lli, |12, VI`|3 land Il@ of alternating current of frequencies FI, F2, F3 and F4 respectively. Ii there is no trouble condition existing in the dial oiice shown in Fig. 3 nonerof relays |52, |63 or lrl is operated. Rel-ay I 62 is operated when any fuse in the dial oiice has burned out; relay E53 is operated when a permanent signal condition exists in the dial office; and relay |53 is operated when any other alarm condition exists in the dial office.

The trunk circuit TC! I, terminating trunk TI in the master cinc-e and the trunk circuit TC|2 terminating the trunk TI in dial office are shown in detail and the operation of each of these trunk circuits is hereinafter described on calls in both directions. The trunk circuit TCZI terminating a trunk to a second dial oiice is similar to the trunk circuit TCE I. The cord CDI and the operators dial and telephone are shown schematically and may be similar to the cord and position equipment disclosed in detail in the patent to King and Miller No. 2,203,765 granted July 23, 1940.

The alarm equipment AL in the master cnice comprises signal receiving relays II, 2|, 3| and lll selectively connected by lters IB, 28, 3i] and 4|) to the jack J I. Each of the filters is tuned to pass current of a diierent one of the frequencies used for transmitting alarm signals from an unattended dial oce to the master oiiice. The alarm apparatus AL further comprises alarm apparatus individual to each unattended oiiice from which alarm signals may be received. The ala-rm apparatus individual to dial olice I comprises keys KII and KIZ, gas-filled discharge lamps LII to Llfl, and a timing relay TRI; the alarm apparatus for a second dial oilce comprises keys KZi and X22, gas-filled discharge lamps L2! to L24, and a timing relay TR2. The lamps LI| and LEI are provided for indicating that there is no trouble existing in the corresponding dial office; the lamps L|2 and L22 are provided for indicating a fuse alarm condition in the corresponding oice; the lamps LI 3 and L23 are provided for indicating a permanent signal condition in the corresponding dial oce; and the lamps LI li and L24 are provided for indicating any other alarm condition which may exist in the corresponding dial omce. The timing relays TRI and TR2 are aranged to operate a predetermined interval, for instance, half an hour after the lighting of any of the associated lamps, so as to extinguish the lamp and thereby indicate that it is time to again check the alarm conditions existingin the corresponding unattended dial office.

The voltage of the .battery B2 normally connected in series with the winding of each of the timing relays and the associated lamps is insucient to effect breakdown of any lamp but is suicient to maintain the energization of any lamp after breakdown until the associated timing relay opens the circuit therethrough. With key KII or -KZI actuated and with any one of relays li, 2|, -35 or lll operated, the voltage of batteries BI and B2 in series is sunicient to break down the lamp corresponding to the operated one of relays lI, 2|, 3| and 4I in the set of lamps 4 associated with the operated one of keys KI I and KEI.

Assume now that a call is originated at station A, that the line finder LFI is operated to extend the calling line to a first selector SI and that the selector SI is actuated in response to the dial impulses created by the dialing of the iirst digit of the called subscribers number to select the terminals .connecting to trunk circuit TCI2. When the cut-through relay (not shown) of the selector SI operates to extend the connection from the conductors of line LI to conductors I 0I and |02 of trunk circuit TCI2, the line relay I II of trunk circuit TCI2 is operated by the curent in a circuit traced from battery through the upper winding of relay IIl, a lower back contact of relay |59,

lower right winding of repeating coil I I 0, another lower back contact of relay |69, conductor |52, middle brushes of selector SI and line nder LFI, lower conductor of line LI, through the telephone at station A, the other conductor of line LI, top brushes of line finder LFI and selector SI, conductor It! I, an upper back contact of relay |59, upper right winding of repeating coil I I0, another upper back contact of relay |09 and through the lower winding of relay I I I to ground. Relay I I l closes a circuit for operating relays |35 and H2. Relay |55 connects ground to conductor |03 to hold the switching relay (not shown) of selector SI and to guard the trunk circuit TC l 2 against seizure lby any other selector having access thereto. Relay II2 connects ground to conductor MSl to start the ringing machine motor (not shown) and closes a connection from the ringing source RG through condenser |55 and a back Contact of relay |84 to conductor IDI so as to transmit a ringing tone to the calling subscriber as -an indication that the operator in the master oice is being signaled. The operation of vrelay |I2 interchanges the connections between the windings of relay II3 and the conductors of trunk TI leading to the master office, thereby reversing the current through `these conductors to effect the operative energization of both windings of the polarized relay 5I of trunk circuit TC! I. Although the windings of relays II3 and 5I are normally connected in a closed circuit over trunk T! the .current in this circuit is not strong enough to operate the marginal relay IIS and is in the non-operate direction with respect to relay 5I, The circuit for operating relay 5I may be traced from battery through the lower winding of relay IIB, a front contact of relay IIE, upper left winding of repeating coil IIB, upper conduc- `tor of trunk TI, upper` back contact of relay 62, upper right winding of repeating coil 59, both windings of relay 5I, lower right winding of repeating coil 59, lower conductor of trunk TI, lower left winding oi repeating coil III), a front Contact of relay l I2, and through the upper winding of relay IIS to ground. The operation of relay 5I closes a circuit for operating relay 52. Relay 52 closes a circuit for lighting the multiple answering lamps 53 and a circuit Yfor operating relay 54. Relay 54 closes a circuit for operating relay 55. Relay 55 closes a circuit for lighting the multiple busy lamps 51 and connects a busy potential through resistor 55 and the upper winding of relay 5l to the sleeve of jack J Ill.

When an operator answers the call by inserting vthe plug P2 of a cord CD5 in jack JIG, a circuit and jack J-I and the lower, high-resistance winding of relay 5i to ground. Relay 51 oper- S ates closing a circuit for operating relay 58. Relay 58 closes a circuit for operating relay 6|; closes a short-circuit around the upper, high-resistance winding of relay I thereby causing the operation of relay IIS of trunk circuit TCI2; opens the busy potential connection between resistor 5B and the sleeve of jack JIU; and opens the circuit through the winding of relay 52 to release this relay and thus extinguish lamp 53. Relay 6I closes a holding circuit for relay 55 and completes the talking connection between the left windings of repeating coil 55 and the line conductors of jack J II).

The aforementioned operation of marginal relay I I3 of trunk circuit TCIZ when the call is answered by an operator in the master oice, closes a circuit for operating relay Izlel. Relay Imi disconnects condenser ISG from conductor IIlI to end the transmission of ringing tone to the calling subscriber, disconnects ground from the ringing-machine motor-start conductor MS, and closes a circuit ior holding relay m5. The talking connection between the calling line and the operator in the master oiiice includes the repeating coils 59 and IIB and the connection is under the joint control of the calling subscriber and the answering operator. When the calling subscriber releases the connection, relay I Il releases.

The release of relay I II causes the release of relay II2, thereby restoring the current over trunk TI to its normal direction to eiiect the release of relay 5I of trunk circuit TCII in the'master office, After relay III releases, relay I55 is held under the joint control of relays H3 and Iill. The release of relay 5I of trunk circuit TCI I connects ground to the upper, low-resistance winding of relay 5l, thereby causing the lighting of the supervisory lamp in the operators cord circuit as a disconnect signal. When the plug P2 of cord CDi is disconnected from jack JIE, relay 5l releases. The release of relay 5l causes the successive release of relays 53 and 6I. Relay 52 reoperates if relay 5I has not yet released. The release of relay 53 opens the short-circuit around the upper, high-resistance winding of relay 5I thereby causing the release of relay H3 of trunk circuit TCI 2. The release of both of relays III and I I3 in trunk circuit TCIZ causes the release of relays IM and HB5. Relay I5 disconnects ground potential from conductor HB3 to cause the release of the selector SI and the return of the selector SI and line finder LFI to normal. The release of relay bld reconnects conductors I3I and |32 to the line relay (not shown) of the incoming selector ISI, thereby preparing trunk TI for seizure on another call in either direction.

Assume next that the operator in the master oilice connects the plug P! of cord CDI with jack J I associated with the alarm equipment AL and connects the plug P2 with jack J I9 to make a call to dial oice I. Relay 5l operates in a circuit including the sleeve conductors of jack J It and plug P2 to battery in the operators position circuit. Relay closes a circuit for operating relay 58. Relay 55 closes a short-circuit around the upper winding of relay 5I to eiect the operation of relay M3 of trunk circuit TCIZ, closes a circuit for operating relay 5I, and connects ground to the upper winding or relay 5l to eiect the lighting of the supervisory lamp in the cord circuit CDI. Relay 5I closes a circuit for operating relay 5a; closes a connection from the winding of relay 54, through the upper left winding of repeating coil 59, to the tip conductor of jack J I0; and closes a connection from ground at the outer lower front contact of relay 58, through resistor 6B, upper back contact of relay 54,inner upper front contact of relay 6I and lower right winding oi repeating coil 59, to the ring conductor oi' jack J I. The operation of relay 54 closes a circuit for operating relay 55; and relay 55 lights the multiple busy lamps 5l, The operation of relay I I 3 of trunk circuit TCIZ closes a circuit, including back contacts of relays m5 and i I2, through the winding of relay HB9. Relay I B9 operates thereby connecting its winding to sleeve conductor |33 of the associated incoming selector ISI and extends ground potential to conductor H13 to mark the trunk circuit TCI2 as busy in the banks of selectors having access thereto. Relay H39 closes a bridge comprising the winding of relay Il and resistor II5 in parallel across conductors ISI and |32 of selector ISI to operate the line relay (not shown) to prepare the selector for operation by dial impulses. The selector ISI connects holding ground potential to sleeve conductor I33 in usual manner to hold relay I 09.

When the calling operator operates the position dial key (not shown), a circuit for operating relay 6G is closed from battery in the position circuit OP through the tip conductors of plug P2 and jack J Ill, a front contact relay 6I, upper left winding of repeating coil 53 and the winding of relay 54 to ground. Relay 54 operates, closing a circuit for operating relay and connecting the tip of jack J I0 through repeating coil 59 to the winding of relay 54, independent of the contact of relay 6I. Relay 65 closes a circuitvior holding relay 54 operated and closes a circuit from ground through the upper winding of relay 52, winding of relay 63, lower front contact of relay 55, lower left winding of repeating coil 59, ring conductors of jack J I5 and plug P2, through the impulse contacts of the operators dial, to battery. Relays'BZ and 63 operate. Relay S2 locks under control of

relays

64 and 58 and opens the circuit through the winding of relay 6 I. The release of relay 6I disconnects the ring conductor of jack J I0 from condenser 5B and short-circuits the upper winding of relay B2 to prepare relay 53 for response to dial impulses. Relay 62 is held operated by the energization of its lower winding in a circuit including its lower front contact, a front contact of relay 64, and a front contact of relay 53. With relays 63 and G2 operated, the impulse repeating contacts of relay 63 are connected across the conductors of trunk TI in place of the bridge comprising the lower winding oi relay 5I. When the operator dials the digits of a called subscribers number, relay 63 is alternately released and reoperated responsive to the dial impulses of each train thereby created. Corresponding impulses are transmitted by the contacts of relay 63 over trunk TI to relay II3 of trunk circuit TC I 2. When dialing is completed, the restoring of the operators dial key disconnects battery from the tip of the cord, releasing relay 65. Relay 64 opens the connection between repeating coil 59 and the tip of jack J I5, shortcircuits the contacts of relay 63, and releases relays 65 and 62. The release of relay G5 disconnects the winding of relay 53 from the ring con- 'ductor of jack J Il! and opens the holding circuit of` relay 54. The release of relay 62 disconnects the contacts of relay 53 from the conductors of trunk TI and reestablishes the bridge, comprising the lower winding of relay 5I, across these conductors. The release of relay 52 causes the reoperation of relay 5I and the completion of the talking connection between jack J I0 and repeating coil 59. The reoperation of relay 6| recloses the circuit for operating relay 54. Since relay 55 is slow in releasing, it remains operated during the transfer of the conductors of trunk TI to and from dialing conditions.

In response to the dial impulses thus transmitted over trunk TI by the contacts of relay 63, relay IIS of trunk circuit TCIZ is alternately released an'd reoperated. When relay IIS releases in response to the first impulse of each train, it opens the bridge across conductors ISI and |32 and closes a circuit including a back contact of relay I I2 and a front contact of relay |59 for operating the sloW-to-release relay Ie'I. With relay II operated, the reoperation of relay IIS closes a bridge comprising resistor |38 across conductors I 3| and |32 in place of the bridge com-l prising the winding of relay IILI. Relay IQ'I is. slow to release and remains operated while a train of impulses is being repeated by relay IIS. The release of relay |21, when relay IIS remains operated at the end of a train of impulses, reconnects the Winding of relay li across conductor: ISI and |32 for response to supervisory signals.

The first train of impulses repeated by reiayc 63 and I I3 controls the operation of the incozr ig; selector ISI to select a corresponding group of terminals. The selector ISI is thereupon operated automatically to select an idle set of terminals in the selected groupl which terminals are connected to a connector CI. The impulses created by the dialing of the last two digits of the called number are repeated by relays |33 and H3 to the line relay ILlI of a connector CI to selectively operate the connector and thereby complete a connection with the called line terminals. If the called line is idle, the called station is signaled in usual manner; and, if the call is answered, relay Idd is operated to reverse the direction of current through conductors ISI and |32 to operate relay IIII. Relay II4 closes a circuit for operating relay IIZ; and relay II2 eects the reversal of current through conductors of trunk TI to operate relay 5I of trunk circuit TCI I. The operation of relay 5I disconnects ground from the upper winding of relay 5l to extinguish the supervisory lamp in the operators cord circuit. The talking connection between the operator and the called subscriber includes the repeating coils 5e and I I5 and is under the sole control of the operator.

If the called subscriber restores the telephone to normal before the operator disconnects, relay |44 releases so as to restore the direction of current through conductors I3I and |32 and thereby cause the successive release of relays I I 4, I I2 and 5 I, and the lighting of the supervisory 'lamp in the operators cord circuit. When the operato-1' disconnects, relays 51, 58, 3|, 54 and 55 are released. The release of relay 5% opens the sliertcircuit around the upper Winding of relay 5I thereby causing the release of marginal relay I I3 in trunk circuit TCI2. The release of relay IIS opens the operating circuit of relayV |639 and opens the bridge across conductors I 3| and |32 thereby causing the release of the incoming selector ISI and the release of the connector CI. If the called subscriber has failed to disconnect, the Vconnector is held operated but the incoming selector ISI is restored to normal in the usual manner. When the called subscriber releases, the connector switch is also restored to normal in usual and Well-known manner.

Assume next that the connector CI has been selectively operated by dial impulses corresponding to the last two digits of the called number to select the trouble checking terminals |50 associated with the alarm equipment ALI. In this case the bridge consisting of the Winding of relay I5| and left winding of transformer |52 effects the tripping of the ringing and closure of the talking circuit through the connector CI in usual manner. If at the time relay I5I operates there is no trouble existing in this dial oiice, none of relays |62, ||I3 and |64 are operated; and a circuit is closed from the alternating current source I'II of frequency FI through a back contact of each of relays |62, |63 and IE5 in series, a front contact of relay I5I, and the right winding of transformer |52 to transmit current of frequency FI through transformer |52 and the talking conductors of connector CI, selector ISI, trunk circuit TCI2, trunk TI, trunk circuit TCII and cord CDI, to the alarm equipment AL in the master office. The current thus transmitted is transmitted through lter I0 to operate relay iI without effecting the operation of any one oi relays 2|, 3| or 4I. If fuse alarm relay |62 is operated, current of frequency F2 is transmitted from source |72 through transformer |52 and the talking connection to effect the operation of relay 2| of alarm apparatus AL in the master oflice, the filter being tuned to pass current of frequency F2. If the permanent signal alarm relay |63 is operated, current of frequency F3 is transmitted from source |13, through transformer |52 and the talking connection to alarm apparatus AL to eiect the operation of relay 3|, filter 30 being tuned to pass current of frequency F3. "And, if other trouble conditions exist in oiiice I such as failure of the ringing equipment, relay |64 is operated and current of frequency FII is transmitted from source I'III, through transformer |52 and the talking connection to alarm apparatus AL to operate relay 4|, the nlter 40 being tuned to pass current of frequency F4. The operator noW momentarily actuates key KI I to connect the signal lamps LII, LIZ, LIS and LIII to conductors I2, 22, 32, 42, respectively.

' The voltage thus applied across the lamp corresponding to the operated one of relays II, 2|, 3| and 4I is high enough to cause ionization. of the gas in that lamp. The operator may then release key KII and disconnect the cord CDI from jacks J I and J I0, the voltage of battery B2 being sufficient to maintain the energization of any one of the signal lamps LII to LI II which has been energized. Thus a continuing signal indicative of the maintenance conditions in the oflice I is given until the timing relay TRI operates. This relay is designed to operate in series with any one of the signal lamps at the end of a desired interval, for instance half an hour. The operation of relay TRI extinguishes the lighted lamp, thereby indicating to the operator that a check of the alarm conditions at the dial ofiice has not been made Within this interval. An energized signal lamp may be extinguished prior to the operation of relay TRI by the operation of the release key KIZ.

A check of the conditions existing in dial office 2 may be made by connecting a cord CDI to jacks J I and J ZI), dialing the trouble checking number for dial office 2 and operating key K2I, thereby effecting the lighting of that one of lamps L2! to L24 which corresponds to the condition existing in dial ofce 2 in similar manner to that in which the alarm lamps for dial cnice I are energized as above described.

What is claimed is:

1. In a telephone system, an unattended dial olce, a master oliice, alarm apparatus in the unattended oflice responsive selectively to a plurality of trouble conditions, signal receiving means in the master oi'lice, means including an interofce trunk for connecting said signal receiving means to said alarm apparatus, and a set of alarm signals in said master oiice controlled by said signal receiving means for visually indicating the existence of any of said plurality of trouble conditions in the unattended oiice.

2. In a telephone system, an unattended dial oiiice, an attended oflice, signal sending means in said unattended office for selectively sending a signal of a first character when no trouble exists in the unattended oce and for sending a signal of a second character when a trouble condition exists in the unattended cmce, signal receiving means in said attended olice for selectively responding to signals of said rst and second characters, means comprising a trunk between said olices connecting said signal receiv ing means to said signal sending means, and visual signal means selectively controlled by said signal receiving means.

3. In a telephone system, an unattended dial office, an attended oiiice, signal sending means in said unattended ofce for selectively sending a signal of a rst character when no trouble exists in the unattended office and for sending a signal of a second character when a trouble condition exists in the unattended office, signal ren ceiving means in said attended oince for selectively responding to signals of said first and sec ond characters, means comprising a trunk between said ofces connecting said signal receiving means to said signal sending means, signal means selectively energized by said signal receiving means to indicate the condition existing in the unattended oice, and means for maintaining the energization of said signal means after the connection between said signal sending and signal receiving means is ended.

4. In a telephone system, an unattended dial oflice, an attended oiiice, signal sending means in said unattended oiiice for selectively sending a signal of a rst character when no trouble exists in the unattended oiice and for sending a signal of a second character when a trouble condition exists in the unattended cnice, signal receiving means in said attended office for selectively responding to signals of said ilrst and second characters, means comprising a trunk between said oices connecting said signal receiving means to said signal sending means, signal means selectively energized by said signal receiving means to indicate the condition existing in the unattended oice, means for maintaining the energization of said signal means after the connection between said signal sending and signal receiving means is ended, and means for terminating the energization of said signai means a predetermined interval of time after the connection between said signal sending and signal receiving means is ended.

5. In a telephone system, an unattended dial oce, an attended office, signal sending means in said unattended oce for selectively sending a signal of a iirst character when no trouble exists in the unattended office and for sending a signal of a second character when a trouble condition exists in the unattended ofce, signal receiving means in said attended oiice for selectively responding to signals of said rst and second characters, means comprising a trunk between said oiices connecting said signal receiving means to said signal sending means, signal means selectively energized by said signal receiving means to indicate the condition existing in the unattended oiice, means for maintaining the energization of said signal means after the connection between said signal sending and signal receiving means is ended, means for terminating the energization of said signal means a predetermined interval of time after the connection between said signal sending and said signal receiving means is ended, and other means for ending the energization of said signal means,

6. In a telephone system, an unattended dial oflice, an attended omce, a trunk between said olces for use in completing connections between calling and called lines, means in said unattended oflice for sending any one of a plurality of signals each of a different character, means in said unattended cnice preparing said signal sending means to send a signal of one character when no trouble condition exists in said unattended oice and for selectively preparing said signal sending means to send a signal of a different character when a trouble exists in the unattended office, the character of the signal depending on the character of the trouble, signal receiving means in the attended office for selectively responding to a signal of any one of said characters, means comprising said trunk for connecting said signal receiving means to said signal sending means, and visual signal means in said attended oiiice selectively controlled by said signal receiving means.

7. In a telephone system, an unattended dial cnice, an attended oice, a trunk between said. offices for use in completing connections between calling and called lines, means in said unattended omce for sending any one of a plurality of signals each of a difierent character, means in said un attended office preparing said signal sending means to send a signal of one character when no trouble condition exists in said unattended office and for selectively preparing said signal sending means to send a signal of a diierent character when a trouble exists in the unattended ofce, the character of the signal depending on'the character of the trouble, signal receiving means in the attended ofce for selectively responding to a signal oi any one of said characters, means comprising said trunk for connecting said signal receiving means to said signal sending means, visual signal means in said attended oilice selectively controlled by said signal receiving means to indicate the condition existing in the unattended omce, and means for maintaining the energization of said signal means after the connection between said signal sending and signal receiving means is ended.

8. In a telephone system, an unattended dial office, an attended oiiice, a trunk between said olices for use in completing connections between calling and called lines, means in said unattended ofce for sending any one of a plurality of signals each oi a different character, means in said unattended omce preparing said signal sending means to send a signal of one character when no trouble condition'exists in said unattended office and for selectively preparing said signal sending means to send a signal of a different character when a trouble exists in the unattended oiiice, the character of the signal depending on the character of the trouble, signal receiving means in the attended oiice for selectively responding to a signal of any one ofv said characters, means comprising said trunk for `connecting said signal receiving means to said signal sending'means, visual signal means in said attendedofce selectively controlled by said signal receiving means, signal means selectively energized by said signal receiving means to indicate the condition existing in the unattended oiiice after the connection between said signal receiving means is ended, and means for terminating the energization of said signal means a predetermined interval of time after the connection between saidA signai sending and signal receiving means is ended.

9. In a telephone system, an unattended dial oflice, an attended office, a trunk between said oiices for use in completing connections between calling and called lines, means in said unattended oice for sending any one of a plurality of signals each of a different character, means in said unattended cnice preparing said signal sending means to send a signal of one character when no trouble condition exists in said unattended ofnce and for selectively preparing saidsignal sending means to send a signal of a different character when a trouble exists in the Vunattended ofce, the character of the signal depending on the character of the trouble, signal receiving means in the attended oice for selectively responding to a signal of any one of said characters, means comprising said trunk for connecting saidsignal receiving means to said signal sending means, visual signal means in said attended oiilce selectively controlled by said signal receiving means to indicate the condition existing inthe unattended oiiice, means for maintaining the energization of said signal means after theconnection between said signal sending and signal receiving means is ended, means for terminating the energization of said signal means a predetermined interval of time after the connection between said signal sending and signal receiving means is ended, and other means for ending the energization of said signal means.

l0. In a telephone system, a plurality of unattended oices, an attended oice, trunks betweensaid attended oince and each of said unattended oiices, like means in each of said unattended ojces for sending a signal of one character when no trouble condition exists in the unattended cnice and a signal of a different character when a trouble condition exists in the unattended oiiice, signal receiving means in the unattended ofiice for selectively responding to a signal of either character, means comprising said trunks for connecting said signal receiving means to the signal sending means in any desired one of said unattended oiiices, like signal means in said attended oiiice for each of said unattended oiilces arranged for selective control by said signal receiving means, and means for connecting the signal receiving means to the signal means corresponding to the unattended cnice the signal sending means of which is connected to said signal receiving means, thereby to effect the selective energization of the signal means.

1l. In a telephone systema plurality of unattended l ofiices, an attended pince, trunks between said .attended oiilce and each of said unattended oices, like means in each ofA said unattended ofces for sending a signalofone Acharacterwhen no trouble condition exists in-the unattended'oiiice and ya'sienal oa different character when a trouble condition exists in the unattended office, signal receiving means in the unattendedoce'for selectively responding to a signal of eithercharacterg means comprisingsaid trunks for connecting said signal receiving means tothe signal sending means in any desiredoneof said unattended ofces, like signal means in said attended cnice for each of said unattended offices arranged for selective control by said signal receiving means, means for connecting the signal receiving means to the signal means corresponding to the unattended oice the signal sending means of which is connected to said signal receiving means, thereby to eiect the selective energization of the signal means, and means in said attended oiiice for each of said signal means for maintaining the energization of the associated signal means after the connection between the signal receiving means and the signal sending means ofthe corresponding unattended oilice is terminated.

12. In a telephone system, a plurality of unattended oiiices, an attended oice, trunks between said attended oihce and each of said unattended offices, like means in each of said unattended cnices for sending a signal of one character when no trouble condition exists in the unattended office and a signal of a diierent character when a trouble condition exists in the unattended office, signal receiving means in the unattended oilice for selectively responding to a signal of either character, means comprising said trunks for connecting said signal receiving means to the signal sending means in any desired one of said unattended omces, like signal means in said attended office for each of said unattended offices arranged for selective control by said signal receiving means, means for connecting the signal receiving means to the signal means corresponding to the unattended oiiice the signal sending means of which is connected to said signal receiving means, thereby to eiect the selective energization oi the signal means, means in said attended ofce for each of said signal means for maintaining the energization of the associated signal means after the connection between the signal receiving means and the signal sending means of the corresponding unattended oice is terminated, and like means in said attended ofce for each of said signal means for terminating the energization of the associated signal means a predetermined interval of time after the connection between said signal receiving means and the signal sending means of the corresponding unattended ofce is terminated.

13. In a telephone system, a plurality of unattended oiiices, an attended oce, trunks between said attended oiiice and each of said unattended oices, like means in each of said unattended ofces for sending any one of a plurality of signals each oi a different character, alarm means in each unattended ofce preparing the signal sending means to send a signal of one character when no trouble exists in the unattended oiiice and for :preparing the signal sending means to send a signal of a different character when a trouble exists in the una tended ofnce, the character of the signal depending on the character of the trouble, signal receiving means in the attended oiiice for selectively responding to a signal of any one of said characters, means comprising said trunks for connecting said signal receiving means to the signal sending means in any desired one of said unattendedofces, sets of signal devices in said attended ofce, one set for each unattended ofce, and means for connecting said signal receiving means to the signal set corresponding to the unattended4 oiiice the signal sending means of which is connected to said signal receiving means, thereby to eiect the selective energization of said set of signal devices.

14. In a telephone system, a plurality of unattended offices, an attended ofce, trunks between said attended office and each of said unattended offices, like means in each of said unattended offices for sending any one of a plurality of signals each of a different character, alarm means in each unattended cnice preparing the signal sending means to send a signal of one character when no troullcle exists in the unattended oiiice and for preparing the signal sending means to send a signal of a.' different character when a trouble exists in the unattended oiiice, the character of the signal depending` on the character of the trouble, signal receiving means in the attended office for selectively responding to a signal of any one of said characters, means comprising said trunks for connecting said signal receiving means to the signal sending means in any desired one of said unattended offices, sets of signal devices in said attended oiiice, one :set for each unattended oiiice, means for connecting said signal receiving means to the signal set corresponding to the unattended office the signal sending means of which is connected to said signal receiving means, thereby to effect the selective energization of said set of signal devices, and means in said attended office for each of said sets of signal devices for maintaining the energizetion of the associated set of signal devices after the connection between the signal receiving means and the Signal sending means of the corresponding unattended office is terminated.

15. In a telephone system, a plurality of unattended ciiices, an attended oiiice, trunks between said attended office and each of said unattended offices, like means in each of said unattended onices for sending any one of a plurality of signals each cf a. different character, alarm means in each unattended office preparing the signal sending means to send a signal of one character when ne trouble exists in the unate tended oihce and for preparing the signal sending means to send. a signal of a different chai acter when a trouble exists in the unattended oiiice, the character of the signal depending on the character of the trouble, signal receiving means in the attended oihce for selectively respending to a signal of any one of said characters, means comprising said trunks for connecting said signal receiving means to the signal sending means in any desired one of said unattended oflces, sets of signal devices in'said attended office, one set for each unattended office, means for connecting said signal receiving means to the signal set corresponding to the unattended oliice the signal sending means of which is connected to said signal receiving means, thereby to effect the selective energization of said set of signal devices, means in said attended oflice for each of said sets of signal devices for maintaining the energication of the associated set of signal devices after the connection between the signal receiving means and the signal sending means of the corresponding unattended ciiice is terminated, and like means in said attended odi-ce for each of said sets of signal devices for terminating the enerw gizaticn of the associated signal devices a predetermined interval of time after the connection between said signal receiving means and the signal sending means of the corresponding unattended oiiice is terminated.

16. In a telephone system, an attended oiiice,

an unattended o'ice, a trunk I'between said ofiices for completing connections between calling and called lines in said omces, signal receiving means in said attended cnice, a trouble checking line in said unattended cnice, means including said trunk for connecting said signal receiving means to said trouble checking line, signal sending means associated with said line comprising a source of current of a first frequency and a source of current of a second frequency, means comprising a trouble alarm relay in said unattended oice for connecting the source of the first frequency to said signal sending means when no trouble exists and for connecting the source of the second frequency to said signal sending means when trouble exists in said unattended oii'ice, said signa-l receiving means comprising two relays and lters for selectively transmitting current of a diiferent one of said frequencies to each of said relays, a signal device for operation when no trouble exists in the unattended office and a signal device for operation when trouble exists in the unattended office, and means for connecting said devices to said signal receiving means thereby to effect the operation of the one or the other of said signal devices according to Whether or not trouble exists in the unattended oince.

17. In a telephone system, an attended oce, an unattended oice, a trunk between said offices for completing connections between calling and called lines in said oflices, signal receiving means in said attended oice, a trouble checking line in said unattended oiiice, means including said trunk for connecting said signal receiving means to said trouble checking line, signal sending means associated with said line comprising a source of current of a first frequency and a source of current of a second frequency, means comprising a trouble alarm relay in said unattended oiiice for connecting the source of the iirst frequency to said signal sending means when no trouble exists and for connecting the source of the second frequency to said signal sending means Vwhen trouble exists in said unattended omce, said signal receiving means comprising two relays and ilters for selectively transmitting current of a diierent one of said frequency to each of said relays, a signal device for operation when no trouble exists 'm the unattended cnice and a signal device for operation when trouble exists in the unattended office, means for connecting said devices to said signal receiving means thereby to eiect the operation of the one or the other of said signal devices according to whether or not trouble exists in the unattended oice, and means for maintaining the operation of either one of the signal devices for a predetermined interval after the connection between said signal receiving means and said trouble checking line is terminated.

18. In a telephone system, an attended oice, a plurality of unattended oflices, each comprising lines including a trouble checking line and switches for seizing called lines, trunks between said attended and each of said unattended ofnces, signal receiving means in said attended ofce, means including said trunks and switches for connecting said signal receivingv means to said trouble checking lines, one at a time, like signal sending means in each of said unattended ofiices associated with said trouble checking lines respectively, each of said signal sending means comprising a transformer, a plurality of sources of alternating current each of a 'diierent frequency, a plurality of alarm relays each operated 115 when 'a diierent trouble condition exists inthe cnice in which the alarm relaysare located and means including said relays for connecting one of said sources to said transformer when no 'trouble condition exists in the office and for connecting another and diierent one of `said sources to said transformer when each dilTerent trouble condition exists inthe oiice, means rsponsive to seizure of said trouble checking line for completing a connection from said line through isaid transformer to one of said sources according to what if any trouble then exists in the oice, thereby to selec- -tively transmit to said signal receiving means a signal indicative of the condition existing in the oiiice, said signal receiving means comprising a plurality of relays one for each different signal which may be transmitted from the signal sending means of a connected one of said trouble checking lines, lters for selectively transmitting current of a different one of said frequencies to each of said rela-ys, respectively, sets of signal devices, one set for each of said unattended ofces and each set including a device for each signal which may be received from the corresponding unattended oiice, means individual to each set of signal devices for operatively con-` necting said devices to said signal receiving means, thereby to effect the operation of the signaldevice corresponding to the condition Vexisting in the unattended oiiice to which the signal receiving means is then connected.

19. In a telephone -system,an attended office, an unattended oice, a trunk between said ofces for completing connections between calling and called lines in said oices, signal receiving means in said attended omce, a trouble checking line in said unattended oiiice, means including said trunk for connecting said signal receiving means to said trouble checking line, signal sending means associated with said line comprising a source of current of a first frequency and a source of current of a second frequency, means comprising a trouble alarm relay in said Vunattended oce for connecting the source of the rst frequency to said signal sending means when no trouble exists in said unattended o'ce and for connecting the source of the second frequency to Said signal sending means when trouble exists in said unattended ofnce, said signal receiving means comprising two relays and lters for selectively transmitting current of a different one of said frequencies to each of said relays, a gas-filled discharge lamp for operation when no trouble exists in the unattended oice and a gas-'lled discharge lamp for operation when trouble exists in the unattended oice, and'means 'for'connecting said lamps to said signal'receiving'means thereby to effect the energization of one or theo'ther of said lamps according to whether or not trouble exists in the unattended oirlce.

20. Ina telephone system, an attendedoliica an unattended oiicega trunk between'said offices for completing connections `between calling and called lines in said oidces, signallreceiving means in said attended ofce, a trouble checking line in said unattended oiice, means including said trunk for connecting said signal receiving means to said trouble checking linea signal sending means associated with said line comprising a source of current of a 'first fleqllerly and a source of Vcurrent of a lsecond frequency, .means comprising a trouble alarm relay in said unattended oice for connecting fthe source of the first frequency to said `signal sending .means when no trouble exists in said unattended oiice and for connecting the source of the Second frequency to said signal sending means when trouble exists in said unattended office, said signal receiving means comprising two relays and filters for selectively transmitting current of a different one of said frequencies to each of said relays, a gas-filled discharge lamp for operation when no trouble exists in the unattended oiice and a gaslled discharge lamp for operation when trouble exists in the unattended office, means for connecting said lamps to said signal receiving means thereby to effect the energization of one or the other of said lamps according to Whether or not trouble exists in the unattended ofce, and means for maintaining the energization of either one of said lamps for a predetermined interval after the connection between said signal receiving means and said trouble checking line is terminated.

21. In a telephone system, an attended office, a plurality of unattended oices, each comprising lines including a trouble checking line and switches for seizing called lines, trunks between said attended and each of said unattended oices, signal receiving means in said attended ofce, means including said trunks and switches for connecting said signal receiving means to said trouble checking lines, one at a time, like signal sending means in each of said unattended oices associated with said trouble checking lines respectively, each of said signal sending means comprising a transformer, a plurality of sources of alternating current each of a different frequency, a plurality of alarm relays each operated when a different trouble condition exists in the oiice in which the alarm relays are located and means including said relays for connecting one of said sources to said transformer when no trouble condition exists in the office and for connecting another and different one of said sources to said transformer when each different trouble condition exists in the oii'ice, means responsive to seizure of said trouble checking line for completing a connection from said line through said transformer to one of said sources according to what if any trouble then exists in the oiiice, thereby to selectively transmit to said signal receiving means a signal indicative of the condition existing in the oiilce, said signal receiving means comprising aplurality of relays one for each different signal which may be transmitted from the signal sending means of a connected one of said trouble checking lines, iilters for selectively transmitting current of a different one of said frequencies to each of said relays respectively, sets of gaslled discharge lamps, one set for each of said unattended o'ices and each set including alamp for each signal which may be received ,from the corresponding unattended office, means individual to each set of gas-filled discharge lamps for operatively connecting said lamps to said signal receiving means, thereby to effect the energization of the lamp corresponding to the condition existing in the unattended cnice to which the signal receiving means is then connected.

22. In a telephone system, an attended oflicev Ya plurality of unattended oiiices, each comprising lines including a trouble checking line and switches for seizing called lines, trunks between said attended and each of said unattended ofiices, signal receiving means in said attended ofce, means including said trunks and switches for connecting said signal receiving means to said trouble checking lines, one at a time, like vsignal 17 sending means in each of said unattended offices associated with said trouble checking lines respectively, each of said signal sending means com prising a transformer, a plurality of sources of alternating current each of a different frequency, a plurality of alarm relays each operated when a different trouble condition exists in the oice in which the alarm relays are located and means including said relays for connecting one of said sources to said transformer when no trouble condition exists in the oice and for connecting another and different one of said sources to said transformer when each different trouble condition exists in the cnice, means responsive to seizure of said trouble checking line for completing a connection from said line through said transformer to one of said sources according to what if any trouble then exists in the oice, thereby to selectively transmit to said signal receiving means a signal indicative of the condition existing in the cfce, said signal receiving means comprising a plurality of relays one for each diierent 18 signal which may be transmitted from the signal sending means of a connected one of said troulilcI checking lines, lters for selectively transmitting current of a dierent one of said frequencies to each of said relays respectively, sets of gas-lled discharge lamps, one set for each of said unattended offices and each set including a lamp for each signal which may be received from the corresponding unattended office, means individual to each set of gas-lled discharge lamps for operatively connecting said lamps to said signal receiving means, thereby to eifect the energization of the lamp corresponding to the condition existing in the unattended office to which the signal receiving means is then connected, and means individual to each set of lamps for maintaining the energization of any lamp in the set for a predetermined interval after the connection of said signal receiving means to the trouble checking line in the corresponding unattended office is ended.

HARRY H. SCHNECKLOTH.