US2355251A

US2355251A - Telephone system

Info

Publication number: US2355251A
Application number: US469090A
Authority: US
Inventors: John G Walsh
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1942-12-15
Filing date: 1942-12-15
Publication date: 1944-08-08
Anticipated expiration: 1961-08-08

Description

Aug. 8, 1944.' J. G. WALSH TELEPHONE SYSTEM Filed nep. 15,; 1942 3 Sheets-Sheet l [III A7' TORNE V Aug. 8, 1944. J, G, WALSH i l 2,355,251

TELEPHONE SYSTEM Filed Dec. 15, 1942 3 Sheets-Sheet 2 co/v/vEc ron NVE/ENTOR J a. WALSH By KCW@ Aug. s, 1944. J, G. WALSH 2,355,251v v TELEPHONE SYSTEM Filed Dec. 15, 1942 s sheets-sheet s FVG 4 CMM ATTORNEY Patented Aug. 8, 1944 TELEPHONE SYSTEM John G. Walsh, Newark, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 15, 1942, Serial No. 469,090

6 Claims.

This invention relates to telephone systems and particularlyto systems arranged for a plurality of classes of service including message rate service.

Objects of the invention are an increase in the efliciency and a decrease in the cost of telephone systems arranged for a plurality of classes of service including message rate service.

It is known in automatic telephone systems to provide a trunk circuit individual to the iii-st selector employed in establishing connections from calling message rate lines for controlling the operation of the calling subscribers register. It is also known to provide means in automatic telephone systems effective to transmit a classof-service indication to the answering operator on special service or intercepted calls. In some arrangements the lines of each class are grouped in the banks of` line-nder switches, the transmission of the class-of-service indication being eiected by actuation of normal post springs on the level or levels in which the lines of a particular class are terminated.

This invention is an automatic telephone system in which the line circuit of a subscribers line includes an additional conductor for indicating the class of service to which the subscriber is entitled so as to allow connection of the line to any set of terminals in the banks of lineiinder switches, and in which the operation of a message rate subscribers meter is controlled over the line conductor which is used to give the classof-service indication. 1= According to another feature of the invention, the line circuit of a message rate subscribers line includes an additional conductor for controlling the operation of the subscribers message register instead of effecting the operation of Athe register by the connection of a booster battery potential to the sleeve conductor used for operating the line cut-off relay thereby to obviate the necessity of providing a booster battery, the additional conductor being further utilized to give a classof-service indication so as to allow connection of afmessage rate line to any set of terminals in the banks of the line-finder switches.

A system embodying the invention and its features is represented schematically in the drawings which form apart of this specication. The invention is not limited to the specic system shown in the drawings but is generally applicable to automatic telephone systems.

Referring to the drawings:

Fig. 1 shows a subscribers station A and line LI, a line circuit LCI, a line `finder LFI, a connector CI, a message rate trunk circuit MRT, and a rst selector SI Fig. 2 shows a connector C2, a line L2 and a subscribers station B;

Fig. 3 shows a trunk circuit TCI connecting a set of terminals in the bank of the selector SI of Fig, 1 to a trunk T; and

Fig. 4 shows a trunk circuit TG2 connecting the trunk T to a jack at an operators position.

Each of the subscriber-s stations A and B is of the usual type employed in common battery systems and includes a dial or other impulse sending device for controlling the operation of switches to establish desired connections. The line finders LFI, selectors SI and connectors C! and C2 are of the well-known two-motion stepby-step type. The line finder LFI, selector SI, and connectors CI and C2 are each represented by a set of `brushes and one or two sets of terminals. Reference may be had t0 pages 53 to 65, inclusive, of the second edition-of Automatic Telephony" by Smith and Campbell 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 T. L. Dimond No. 2,210,068, granted August 6, 1940, for a description of the operation of a twomotion step-by-step line-nnder switch.

Assume now that a call is initiated at station A, the line relay I of line circuit LCI being energized in series with the conductors of line LI to actuate its outer frontcontacts, thereby con.- necting ground to conductor I'I to start an idle line nder and connecting the middle winding of -relay I0, through conductor I3, to the test terminals of the line circuit LCI in the banks of a group of line lindern including the finder LFi. Assuming the iinder LFI to be the nder which `is operated, the middle winding of relay IB is energized to fully operate relay I0 when the test brush 23 engages the terminal to which conductor I3 is connected and the line nder is stopped with its brushes 2|, 22, 23 and 2.4 in engagement with the terminals to which conductors II, I2, I3 and I4 of line circuit LCI are connected. As soon as the eut-through relay (not shown) of line inder LFI is operated, as Vdescribed in vthe aforementioned patent to T. L. Dimond, the line LI is connected through conductors II and -I2, brushes 2l and 22, and the windings of supervisory relay 3U of message rate trunk circuit MRT to the line relay (not show-n) of selector SI. Holding ground potential is thereupon connected to sleeve conductor 2l in usual manner -to hold the line nder LFI in operated position and to maintain the operative energizationof the middle winding of relay I. The complete operation of relay I disconnects the conductors o line LI from the outer windings of relay Iii and disconnects ground from start conductor I1. Relay 39 is polarized and the current through its windings is ineffective to cause its operation at this time. If the calling line is a message rate line, a register I is connected to the terminal engaged by brush 24; if the calling line is one of a second class of lines, ground is connected through a resistor I6 to the terminal engaged by brush 24 as shown in Fig. 1A; or if the calling line is one of a third class there is no connection to the terminal engaged by brush 24. 'If the calling line is a message rate line, the winding of class-of-service relay 25 is connected through conductor 2D, brush 211 and conductor i in seriesY with register I5; and relay 25 is thereby iully energized to actuate all of its contacts, but register I5 is marginal and does not operate at this time. If the calling line is one having a resistor I6 connected to the terminal engaged by brush 24, relay 25 is only partially energized; and, if the calling line is one of the third class, relay 25 remains normal. lf relay 25 is operated completely, it locks through conductor 21 to holding ground potential in the selector SI, connects -ground to conductor 29, and connects grounded conductor 21 directly to conductor 28; if relay 25 is operated only partially, grounded conductor 21 is connected to conductor 28 through resistor 26; and if relay 25 remains normal, there is no connection oi ground potential to conductor 2S.

When the calling line is connected to selector SI, dial tone is transmitted to the calling station A, in usual manner, to indicate that the subscriber may start dialing, When the calling subscriber dials the rst digit, the brushes of selector SI are stepped up to the level corresponding to the digit dialed and the brushes are thereupon advanced step by step to select an unguarded set of terminals in the selected level. Assuming this call to be one for another subscriber inthe same dial oliice, the selected set of terminals 4U is connected through

conductors

4I, 42 and 43 to an intermediate selector (none shown) or directly to a connector C2, as shown in the drawings.' Upon extension of the connection to a connector C2, the line relay E5 is operated in series with the calling line LI. Relay 45 closes a circuit for operating slow-torelease relay 4; relay Iii connects holding ground potential, through conductor 63, to the -terminal engaged by brush 31 to hold the selector SI, to hold relay 25 if operated, to hold the line nder LFI, and to maintain the energization of the middle winding of relay I0. Relay d5 responds to the trains of impulses created by the dialing of the line selecting digits of the called subscribers number, thereby eiecting the operation of the connector to establish conection with the called line L2. The called line is tested and, if idle, the ringer at the called station B is operated. All of these operations are eiiected in usual and well-known manner. When the call is answered, relay 46 is operated thereby interchanging the connections between the windings of relay 45 and conductors @I and 42 vso as to reverse4 the direction of the current through the windings of supervisory relay 39 of trunk circuit MRT and thereby cause the operation of relay 39. AIf the calling line is a line other than a message rate line and relay 25 is not completely operated, the operation of relay 39 is without eiect. But, if the calling line is a message rate line so that relay 25 is fully operated, a circuit for energizing the upper winding of relay 3| is closed when relay 30 operates or as soon thereafter as ground is next connected to conductor 29 by the interrupter which is common to all of the message rate trunk circuits. The interrupter intermittently connects ground to conductor 29, for instance for onehalf a second out of every two and a half seconds. The energization of the upper winding of relay 3i effects the actuation of its outer lower front contact without actuating its other contacts. The lower winding of relay 3I is thereby connected to conductor 21 in series with the upper winding but, as long as ground is connected to conductor 29, the lower winding of relay 3I is short-circuited. AS soon after relay 3l is partially operated as ground is disconnected from conductor 29, both windings of relay 3| are energized in series and the complete operation of this relay is thereby effected. At its outer upper front contact, relay SI connects the winding of relay 32 to conductor 29; and, as soon as ground is next connected to conductor 29, relay 32 operates. Relay 32 locks directly to grounded conductor 21, disconnects ground from conductor 20, connects battery through resistance 33 to conductor 20 to operate the marginal register I5 of the calling line, disconnects the windings of relay 3l from conductor 21 and connects these windings to conductor 29. Relay 3l is thereby held operated until ground is next disconnected from conductor 29. When relay 3l releases, battery is disconnected from conductor 2G to release the register I5 and ground is reconnected to conductor 20. The connection between stations A and B is maintained until the telephone set is restored to normal at station A, whereupon relay 45 is released; and so also is relay 39, if operated. The release of relay causes the release of relay 44. Relay 44 disconnects ground from conductor 43, thereby effecting the release of the selector SI, the release of

relays

25 and 32, if operated, the release of line nder LFI and the release of relay I0. If the telephone at station B is also restored to normal, the connector C2 returns to normal in usual manner. f

Assume neXt that the subscriber at station A initiates a call to an operator, in which case the dialing of the digit 0 (or any other digit which is used as the code for calling an operator) causes the selector SI to select a set of terminals 50 in the corresponding level of its bank, which set of terminals is connected to an idle trunk circuit TCI associated with a trunk T leading to an operators position. When the cut-through relay (not shown) of selector SI operates, the connection from the calling line is extended through

brushes

35, 36, 31 and-38 to trunk circuit TCI, thereby efecting the operation of line relay 89. The circuit for operating relay 89 is traced from battery through the right winding of relay B9, inner upper back contact of relay 81, upper left winding of repeating coil RCI, another back contact of relay 81, conductor 52, brush 36 of selector SI, lower winding of relay 39, brush 22 of line finder LFI, conductor I2 of line LI, through the telephone set at station A, conductor II of line LI, brush 2I of line iinder LFI, upper winding of relay 30, brush 35 of selector SI, conductor 5I, a back contact of relay 81, lower left winding of repeating coil RCI, inner lower back contact of relay 81, and the left winding of relay 89 to ground. Relay 30 does not operate since the current through its Windings is in the non-operate direction. Relay 89 closes circuits for operating relays 84 and 90.`

Relay 84 connects ground to conductor 53 to guard against seizure of trunk circuit TCI by any other selector, to hold selector SI and line inder LFI, to hold relay 25, if operated, and to hold relay I operated. Relay 84 also closes a connection between condenser 9| and conductor 52 for transmitting ringing tone to the calling subscriber to indicate that an operator is being signaled. Relay 90 interchanges the connections between the windings of relay 86 and conductors 9'! and 98 of trunk T leading to an operators position thereby effecting the operative energization of both windings of polarized relay |00 of trunk circuit TG2 at the distantend of trunk T. Although the windings of relays 86 and |00 arev connected in a normally closed circuit over trunk T, the current is not strong enough to operate the marginal relay 8G and is in the non-operating direction with respect to relay |00, The operation of relay |00 closes a circuit for operating relay I 0I; relay I 0I closes a circuit for operating relay |02; and relay |02 closes a circuit for operating relay I 03. Relay |0| also closes a circuit for lighting answering lamp `I I3. Relay |03 closes a circuit for lighting busy lamp IId and connects a busy potential, through resistor H8 and the lower winding of relay |05, to the sleeve of jack IIZ.

lf the call is from a message rate line, relay ,83 is fully operated due to the complete operation of relay 25 as hereinbe'fore described. If relay 25 is only partially operated, resistor 2S limits the current through

conductors

28 and 54 to only partially operate relay 83; and, if relay 25 is not operated, relay 83 remains normal. With relay 83 completely operated, tone source T2 is connected to condenser T; and with relay 83 only partially operated, tone source TI is connected `,to condenser T. With relay $33V either partially or fully operated, a circuit is closed for operating slow-to-release relay 82.

When an operator answers the call by inserting the plug of a cord in jack II2, a circuit is closed from battery in the operators position circuit through the sleeve conductor of the answering cord and jack I I2 and the upper winding of relay |05. Reference may be had to Patent No. 2,209,777 granted to R. E. King et al. July 30, 1940, for a disclosure of cord and position circuits arranged for cooperation with the trunk circuit TG2. Relay |05 operates, closing a circuit for operating relay |03. Relay |06 closes a circuit for operating relay |01; closes a short-circuit around the high resistance, upper winding of relay |00, thereby causing the operation of relay 86 of trunk circuit TCI; and opens the circuit through the winding of relay IOI to release this relay and extinguish lamp II3. Relay |01 closes a holding circuit for relay |02 and completes a talking connection between the right windings of repeating coil RC2 and the line conductors of jack II2.

The aforementioned operation of marginal relay 88, when the call is answered, closes a circuit for operating relay 80. Relay 00 disconnects condenser 9| from conductor 52, to end the transmission of ringing tone to the calling subscriber, and causes the release of relay 82.

While relay 82 is releasing, a class-of-service tone is transmitted through condenser T and front contact of relay 82 to conductor 52, thence through repeating coils RCI and RC2 to the answering operator to indicate the class of the calling subscriber. If relay 83 is operated completely, the tone is from source T2; if relay 83 is .partially operated, the tone is from source TI; and if relay 8,3 is normal, no tone is `transmitted.

VThe talking connection between the station A and operator includes repeating coils RCI and RC2 and the connection is under the joint control of the calling subscriber .and answering operator. When the telephone at station A is restored to normal, relay 89 releases vthereby causing` the release of relay 90 so as to restore the current over trunk T to its normal direction and thus effect the release of relay |00 of trunk cir- `cuit TC2. When relay |00 releases, it connects ground to the lower, low resistance winding of relay |05 thereby causing the lighting of a supervisory lamp in the operators cord circuit as a disconnect signal. When the operator disconnects, relay |05 releases causing the successive release of relays |06 and I0'I. Relay I0IV reoperates if relay |00 has not released. The release of relay |05 opens the short-circuit around the upper, high resistance winding of relay |00 thereby causing the release of relay of trunk circuit TCI. release of relay 80. When both the calling subscriber and answering operator have released the connection, relay 84 releases, thereby disconnecting ground potential from conductor 53 to effect the release of selector SI, line finder LFI and relay I0.

What is claimed is:

l. In a telephone system, subscribers lines including message rate lines, means including a trunk circuit interconnecting a callingY message rate line and a called line, said trunk circuit comprising a class-o-service relay, a message register for said calling line, the connection between the calling line and trunk circuit comprising a conductor interconnecting said message register and said class-of -service relay thereby to operate said relay, said register being marginal to prevent its operation in series with said relay, and means including contacts of said relay for operating said register responsive to the answering oi the call at the subscribers station on the called line. v

2. In a telephone system, subscribers lines including message rate lines, a message register for each of said message rate lines, a trunk circuit, means responsive to the initiation of a call on one of said lines for connecting the calling line to said trunk circuit, an operators position, means including subscriber controlled switching means for selectively connecting said trunk circuit with alcalled subscribers line or with said operators position, relay means in said trunk circuit,` means comprising the message register of a calling message rate line connected to said trunk circuit for selectively operating said relay means to indicate that the calling line is a message rate line, means comprising means individual to a line, other than a message rate line, connected to said trunk circuit for selectively operating said relay means to indicate that the calling line isnot a message rate line, and means including said relay means in said trunk circuit for effecting the operation of the message register of a calling message rate line connected to said trunk-circuit in response to the answer of a call to one of said subscribers lines.

3. In a telephone system, subscribers lines in- The release of relay 86 causes the cluding message rate lines, a message register for each of said message rate lines, a trunk circuit, means responsive to the initiation of a call on one of said `lines for connecting the calling vline to said trunk circuit, an operator-s position, means including subscriber controlled switching means for selectively connecting said trunk circuit with a called subscribers line `or withsaid operators position, relay means in said trunk circuit, means comprising the message register of a calling,r message rate line connected i toV said trunk Icircuit for selectively operating said relay means to indicate that the calling line is a message rate line, means comprising means individual to a line, other than a message rate line, connected to said trunk circuit for selectively operating said relay means to indicate that the calling line is notv a message rate line, means including said relay means in said trunk circuit for effecting the operation of the message register of a calling message rate line connected to said trunk circuit in response to the answer of ra call to one ol said subscribers lines, and means selectively controlled by said relay means in said trunk circuit on a call to said operators position for indicating to the answering operator the character of the calling line.

V4. In a telephone system, subscribers lines of different classes including message rate lines, a message register for each of said message rate lines, a trunk circuit, means responsive to the initiation of a call over one of said lines for connecting the calling line to said trunk circuit, class of -service relay means in said trunk circuit, means including the message register of a message rate line connected to said trunk circuit for selectively operating said class-of-service means to indicate that the connected calling line is a message rate line, means including means individual to a line of another class connected to said trunk circuit for selectively operating said class-of-service means to indicate that the call is from a line of said other class. an operators position, switching means controlled by the calling subscriber over the calling line and said trunk circuit in series for completing a connection with a. called subscribers line or with said operators position as desired, means selectively operated under the control of said class-of-service relay means in said trunk circuit for giving to the answering operator on a call to said position an indication of the class of the connected calling line, and register operating means in said trunk circuit operatively responsive to the answer of a call though said trunk circuit to a called subscribers station, the selective operation of said class-of-service relay means being effective to connect said register operating means to the register of a calling message rate line.

- 5. In a telephone system, subscribers lines of a plurality of classes, the lines in one of said classes being message rate lines, a message register for each of said message rate lines, the winding of Yeach of said registers having low electrical resistance, a resistor'individuai to each line in another of said classes, eachof said .resistors having a substantially higher resistance than each of said registers, a trunk circuit, means responsive to the initiation of a call over any one of said lines for connecting the calling line to said trunk cir- Cil sage rate line, said connecting means comprising talking conductors, a holding conductor and a control conductor, said control conductor connecting said class-of-service relay in series with the message register of a connected calling message rate line to fully operate said class-of-service relay in series with said register without operating said register, saidcontrol conductor connecting said class-of-service relay in series with the individual resistor of a connected calling line of said other class to partially operate said classoi`service relay, the partial operation of said class-of-service relay being ineffective and the complete operation of said class-of-service relay being eiective to close a locking circuit, to clisconnect the relay from said control conductor and to connect said control conductor to said relay means, and answering supervisory means in said trunk circuit for operating said relay means thereby to eiTect the closing of a circuit through said control conductor for operating the message register of a connected calling message rate line.

6. In a telephone system, subscribers lines of a plurality of classes, the lines in one of said classes being message rate lines, a message register for each of said message rate lines, the winding of each of said registers having low electrical resistance, a resistor individual to each line in another of said classes, each of said resistors having a substantially higher resistance than each of said registers, a trunk circuit, means responsive to the initiation of a call over any one of said lines for connecting the calling line to said trunk circuit, said trunk circuit comprising a class-ofservice relay and relay means for use in operating the message register of a connected calling message rate line, said connecting means comprisn ing talking conductors, a holding conductor and a control conductor, said control conductor connecting said classofservice relay in series with the message register of a connected calling message rate line to fully operate said class-of-service relay in series with said register without operating said register, said control conductor connecting said class-of-service relay in series with the individual resistor of a connected calling line of said other class to partially operate said class-of-service relay, the partial operation of Asaid class-of-service relay being ineffective and the complete operation of said class-of-service relay being eiective to close a locking circuit, to disconnect the relay `from said control conductor and to connect said .control conductor to said relay means, an operators position, subscriber controlled switching means for establishing connections between calling lines and called lines and between calling lines and said operators position, each of said connections including said trunk circuit,means selectively controlled by said classof-service relay for indicating to the answering operator the class of the connected calling line on a call to said position, means including a supervisory relay in said trunk circuit for operating said relay means responsive to answer of a cali to a called subscribers line, the complete operation of said class-of-service relay and the operatlonof said relay means being effective to close a cir-cuit through said control conductor for operating the message register of a connected calling message rate line.

J OHN G. WALSH.