US2005590A - Telephone system - Google Patents

Description

, June 18, 1935. MESZJAR 2,005,590

TELEPHONE SYSTEM Filed se i. .29, 1934 2 Sheets-Sheet 1 J1me 11.8, 393.5. J. MESZAR TELEPHONE SYSTEM Filed Sept. 29, 1954 2 Sheets-Sheet 2 oQooQ /NVE/VTOR J. MESZAR TTORNEY- Patented June 18, 1935 UNITED STA'iEd rarest" orrlcs TELEPHONE SYSTEM Application September 29, 1934, Serial No. 746,035

Claims.

5 same line circuit, for example, either a so-called inward or completing operator, or a through operator depending upon the nature and destination of the call.

In the well-known ringdown method of operating toll lines, it is the usual practice to have all the incoming line signals appear at the inward or completing operators position and when through positions are provided, multiple the incoming lines to such positions. Line signals are also provided at such through positions but are not controlled by the outward operator, instead they are controlled from the inward position. Therefore, the inward operator receives all calls and if the destination of a call is such' as to require the attention of the through operator, the inward operator transfers the call by performing an operation which actuates the line signal at the through position associated with the multiple appearance of the line on which the call is waiting. Observing this line signal the through operator connects with the line in the usual manner and extends it as desired.

The patent to R. S. Bailey et al. 1,860,446, dated May 31, 1932 discloses a straightforward toll line system employing alternating current, having a frequency within the voice range, for operating the calling and supervisory signal apparatus. In that system the initiation of a call at an outward position, results in transmitting current of a certain frequency over the line to the distant o ifice where it causes apparatus to function to operate a call lamp and also to transmit an answerback or cut-off signal to the outward or originating position. When this cut-off signal is received at the outward position, it immediately causes apparatus to function to stop the transmission of the connect signal current.

erator may selectively signal either the inward or through operator as desired.

An object of the invention is, therefore, to en able an outward operator to selectively signal either one of two different classes of operators over the same line.

A feature of the invention whereby the fore going object is attained resides in the provision of means in connection with the system disclosed in the before referred to Bailey Patent 1,860,446 whereby the means normally responsive to the cut-off signal is made slow to operate thereby introducing a short delay in cutting off the connect signal from the line and by the provision of other means whereby the outward operator may change the circuit connections to accelerate the operation of the cut-off apparatus to shorten the normal duration of the connect signal impulse sufiiciently to cause apparatus at the distant office to function to prevent normal operation of the line signals at the inward position and cause the line signals at the through position to operate instead.

The invention will be understood from the following description when read in connection with the accompanying drawings:

Fig. 1 of which represents an outward operators position and the portion of the line located thereat; and

Fig. 2 represents apparatus at the distant oflice where the line is arranged to terminate at different positions, i. e., at an inward position and also at a through position. a

It will be first assumed that the outward operator, Fig. l, desires to obtain a connection which would be handled by the inward or completing operator'at the distant ofiice. She will, therefore, insert the calling plug l of toll cord TC in jaci; 2 of the toll line L after having first operated the usual talking key 3 which causes the obvious operation of relays t and 5. The operation of relay 5 in turn causes relay 1 to operate in a circuit which can be traced from a high resistance ground (not shown) on the sleeve of jack 8 with which the answering plug 9 of the cord circuit has been previously connected, sleeve conductor of plug 9, operated contacts iii of relay 5 and windings of relays 5 and 1 to battery. Relay 6 is marginal and does not operate under this condition. The operation of relay i caused the obvious operation of relay i I, which at its left-hand contacts completed the connection of the operators telephone set OT across the talking conductors of the cord circuit by way of contacts i2 and it of relay 4 which was operated in response to the actuation of the talking key 3. Another connection to said operators telephone circuit is made from ring conductor of plug l, through lower operated make contacts of relay 4, normally closed left-hand contacts of relay 88 to conductor i and from tip conductor of plug I through upper inner make contacts of relay l, operated left-hand contacts of relay 8? to conductor 89. Relay 01 operates as will be hereinafter explained. Relay H in operating also closed a circuit traceable from battery through supervisory lamp 85, upper inner operated make contacts of relay 5, high resistance 03 to ground on right-hand operated contacts of relay H. Lamp 8| is not lighted under this condition.

t will now be observed that with plug l in jack 2, a source of battery potential is is con- 7 nected to the sleeve conductor l of the toll line, which can be traced from battery i l, through normally closed contacts of relay l6, windings of relay H and marginal relay l8, operated contacts R0 of relay 5, over sleeve conductors of plug l and jack 2 and conductor E5 to ground through the winding of sleeve relay 20. Relays H, ill and 20 operate in this circuit. Relay ll operates through an obvious circuit relay 8?. Relay l8 in operating connects a low resistance 85- to ground and relay 8? connects to ground a high resistance 85. These two resistances in multiple are also connected through the lower, inner oper ated make contacts of relay 5 to battery through calling supervisory lamp 82, which lights. Marginal relay i8 operated in the circuit above traced due to the low resistance condition of the winding of sleeve relay 20, which winding consists of separate low resistance and high resistance sections. For descriptive purposes only a single winding is shown in the accompanying sketch and the circuit details whereby the effective resistance of the winding is changed from high to low are omitted as this method of obtaining supervision on toll lines is well-known in the art and is disclosed in above mentioned patent to R. S. Bailey et a1. 1,860,446, Fig. l, as shown by the functioning of relay E02 in said patent. Relay 20 in operating operates relay 23 which operates through an obvious circuit line busy signal 28. Relay 20 also operates relay 25 through a circuit traceable from ground on the operated contacts of relay 20, through the left-hand normally closed'contacts of relay 22, outer righthand normally closed contacts of relay 25 and winding of relay 26 to battery. Relay 26 locks to ground on the contacts of relay 24 over a circuit traceable from battery through the winding of relay 20, left-hand and righthand outer operated contacts of relay 26, through normally closed contacts of relay 24 to ground. Relay 20 in operating operates relay 25 through a circuit traceable from battery through right-hand winding of relay 25, right-hand inner and outer operated contacts of relay 20 to ground on normally closed contacts of relay 24. In operating, relay 25 operates through an obvious circuit, relay 9'! which disconnects line conductors 35 and 31 from conductors 3t and 38, respectively, and connects them to a source 30 of voice frequency current of 1400 cycles modulated at a 20 cycle rate. This circuit is traceable from 1400/20 cycle current source 30 through right-hand inner operated make contacts of relay 25, through lower operated make contacts of relay 0? to conductor 31, thence through resistance 33 and in multiple with coil 39 of the directional selection circuit arrangement 90 to conductor 40 of toll line L. Returntube 50.

ing over conductor ll, the circuit is further traced through coil 34 and resistance 32 in multiple, over conductor 35, through upper operated make contacts of relay ill and the left-hand outer operated make contacts of relay 25 to point of beginning at source 30 of the 1400/20 cycle current.

The aforesaid direction selection circuit arrangement is disclosed and claimed in the patcut to George Crisson 1,755,243 issued April 22, 1930 and, as it forms no part of the present invention, it is deemed sufficient to state that this arrangement is constructed and arranged as to prevent any portion of the voice frequency current from source 30 applied to the line L by relay fil from flowing over leads 02 and 43 into the receiving circuit RC2 while at the same time diverting voice frequency signals received over the line from the other end and transmitting them without attenuation to the signal receiving circuit RC1. It will therefore be understood that the 1400/ cycle signal, transmitted over the line as a calling or connect signal is not impressed on the signal receiving circuit RCI but that signals transmitted from the distant end, are shunted into receiving cricuit RC! to cause the functioning of apparatus as will be hereinafter described.

When the 1400/20 cycle current is transmitted over conductors 00 and M of the toll line to the distant oiiice it enters over conductors 08 and 09 cf Fig. 2 and is transmitted through coils M and 45 of the directional selection circuit arrangement 40, (which is similar to that at the outgoing end of the toll line) over conductors ll and 00 to receiving circuit RC2. The incoming 1100/20 cycle signal is here detected by detector vacuum tube 19 and amplified by vacu- The 20 cycle output of tube 50 is transmitted through transformer 53 to the winding of polarized relay 52, the armature of which is caused to vibrate at a 20 cycle rate. This causes the full Wave rectifier RI, which is an arrangement well-known in the art and need not be described here, to deliver a unidirectional current to relay 5! which operates, Relay 5| in operating operates, through .an obvious circuit, relay 54 which in turn operates relay 55, thereby operating relay 50 and starting the operation of slow operating timing relay 51, through a, circuit traceable from battery through resistance 58, left-hand operated make contacts of relay 55, resistance 50 to ground through the winding of relay 5?. The operating circuit for relay 55 is traced from groundon the operated contacts of relay 54 through the winding of relay 55 to battery and for relay 56 from ground through the winding of relay 56, right-hand inner operated make contacts of relay 55 to battery. Relay 55 in operating also operates relay 84 through a circuit that may be traced from battery through the winding of relay 84, righthand outer operated make contacts of relay 55 to ground, Relay 04 operates relay 6| through an obvious circuit and connects 1000/ cycle current to the toll line over a circuit that may be traced from source 60 of 1000/30 cycle current through right-hand outer operated contacts of relay 34, and upper operated make contacts of relay 6! to conductor 62 and from source 04 through left-hand operated contacts of relay at, and lower operated make contacts of relay Eil to conductor 63. From conductors 62 and 63 the 1000/30 cycle current passes through the directional selection circuit arrangement 46 including resistances 65 and 66 to toll line conductors 9B and 59. No current from source 54 passes into the receiving circuit RC2. From conductors 9 .3 and 9B the 1000/30 cycle current passes over the toll line and conductors l and il at the originating end (Fig. 1), through the directional selection circuit arrangement 90 and over conductors t2 and 63 into receiving circuit RCl which is similar to receivingcircuit RC2 previously described with the exception that this circuit is tuned to respond to 1000/30 cycle current. Relay it? accordingly operates and operates relay 23 through an obvious circuit. Relay 23 in operating starts the operation or" slow operating timing relay 2'! through a circuit that may be traced from battery 68 through resistonce 69, right-hand inner operated contacts of relay 23 and winding of relay 2! to ground. Relay 23 also closes a circuit for operating relay 122, which may be traced from battery on the operated inner make contacts of through winding of relay 22 to ground on the left-hand operated make contacts of relay 23. Relay 212 looks to ground through an obvious circuit. After an interval of about 0.6 second relay 2i operates through the circuit hereinbefore traced and operates relay 24 through a circuit traceable from battery on the contacts of relay El, through winding of relay 24 to ground on the right-hand operated outer contacts of relay 23. Relay M .in operating disconnects the holding ground for relays 25 and 26 which release. Relay 25 in releasing disconnects the source 30 of 1400/20 cycle signaling current from the leads connected to the front contacts of relay 9'! and also opens an obvious circuit through the winding of relay 91, which releases and reconnects conductors 35 and 3'? to conductors, 35 and 38 respectively.

As a result of the above described circuit action the connect signaling current of 1400/20 cycles from source 30 was not disconnected until after the operation of slow-to-operate relay 271.

During this delay interval from the time the 1400/20 cycle current is sentout until said slow operate relay 2'! operates, which interval can be conveniently adjusted for approximately one second, slow operate relay 53' of Fig. 2 at the incoming end has had time to operate and cause the operation of relay 10 through a circuit traceable from battery on the operated contacts of relay El through the winding of relay "lit to ground on the operated contacts of relay t l. Relay is in operating operates relay 1! through a circuit traced from battery on the operated contacts of relay l0 through the lower winding of relay H to ground on the normally closed lower contacts of relay l2. Relay H in operating lights the cord circuit lamp [3 of the cord circuit IC at the inward toll position, through a circuit traceable from battery on the lower outside operated contacts of relay ll, through the lower closed contacts of relay l4 and lamp it to ground. Relay 'il in operating also closes an obvious, circuit through the winding of relay M to the sleeve conductor of plug l of inward cord circuit IQ and locks through a circuit traceable from battery on the right-hand closed contacts of relay 16 through upper inner operated contacts and upper winding of relay "H to ground on the lower closed contacts of relay "l2. Relay H in operating also removes ground on its upper outside contacts from the lower winding of relay l2, thereby preventing the operation of relay l2 and the false lighting of lamp 96 as the through porelay 2 i :sition after the disconnection of the MOO/20 cycle current at the outgoing toll ofiice as hereinbefore described causes the release of relay ill of receiving circuit RC2. The release of relay 5! causes the subsequent release of relays cs, 55, 70, 57,04 and ti. Relays 84 and GI in releasing di connect the source 64 of answer-back 1000/39 cycle current from the toll line. Relay ti recon.- nects line conductors 62 and t0 and 63 and it, thereby restoring the normal continuity of the conversational path.

In response to the call coming in on inward cord circuit IC telephone circuit 0T2 is connected to conductors H and 18, thereby enabling the inward operator to converse over the toll line with the originating operator. The circuit details of said telephone circuit 0T2. with the particular circuit means that may be used for effecting the connection are well-known in the art and need not be shown here. After obtaining the number of the called line, the inward operator completes the connection by plugging into the jack of a trunk not shown over which conne tion with the line of the called subscriber may be made. When the inward operator inserts plug 15 into said trunk jack ground on the sleeve conductor operates relay M through the lower operated inner contacts of relay ll. Relay M in operating extinguishes lamp 13 by opening at its lower outside contacts the energizing circuit for said lamp hereinbef'ore traced and also connects conductors Ti and "it through its upper contacts and lower inside contacts to the tip and ring conductors of plug l5, thereby extending the talking connection from the originating ofiioe to the trunk (not shown) leading to the office at which the line of the called subscriber terminates. The trunk operator at the terminating office now completes the connection to the called line according to well-known traffic methods and supervision is transmitted to the originating office using the source at of 1000/30 cycle current as the means of transmission for controlling the resistance of sleeve relay 20 at the originating end as hereinbefore explained. The circuit details required for establishing the final connection to the called line and for supervision are not shown since these are not a part of this invention. Bailey Patent 1,860,446 aforementioned discloses circuit details illustrative of a method that may be used.

When the subscriber at each end of the corn nection hereinbefore described disconnects, the grounded resistance connected to the sleeve conductors of jacks 2 or 8 is changed from high to low by circuit arrangements not shown, as stated hereinbefore, thereby causing the lighting of lamps 52 and 81 as disconnect signals. In the case of lamp 8! low resistance ground is effective through the upper normally closed contacts of relay 5, if relay 5 is not operated at the moment or disconnection. If relay 5 is operated, then marginal relay 2- operates through the circuit hereinbefore traced for operating relay '1. Relay 0 in operating connects low resistance 100 in mul tiple with high resistance 03, and these two resistances togethercause the lighting of lamp 8| through the upper inner operated make contacts of relay 5. In the case of lamp-82, if relay 5 is normal at the time of disconnection, the low re sistance of sleeve relayZE at this time is effective to cause the lighting of lamp 82 through the lower normally closed contacts of relay 5. If relay 5 is operated at the time of disconnection then marginal relay 18 operates through the circuit here inbefore traced for operating relay I'I. Relay 18in operating connects low resistance in multiple with high resistance 86 and these two resistances together cause the lighting of lamp 82 through the lower inner operated make contacts of relay 5. When the originating operator observes the lighted condition of lamps 2| and 82, plugs 9 and I are withdrawn from jacks 8 and 2 respectively which extinguishes lamps 8d and 82. Sleeve relay 20 also releases, releasing thereby relays 2! and 22 and restoring busy signal 28 to normal. At the time the disconnect signals are received, if talking key 3 is operated, and likewise relays 4 and 5, sleeve controlled relays 6, I, II, I8, I"! and 3? also release when the plugs are withdrawn. All apparatus at the originating end is now restored to normal. At the terminating end of the connection, relay '56 functions when a disconnect signal is received and opens the locking circuits for relays 56 and ll which release. Relay "H in releasing, releases relay "M. The circuit arrangement for the release signal and for relay "Eli are not shown, as these details are well-known, are not a part of the invention and are not required for its description. When the inward operator removes plug ?5 from the trunk jack (not shown) all apparatus is restored to normal.

The description hereinbeforegiven was for a call requiring the attention or" the operator at the inward position of the toll switchboard. The operation of the invention for a call requiring the attention of the operator at the through position .will now be given.

In response to the line signal (not shown) the operator inserts plug 8 into jack 8 and then opcrates the talk key 3 which connects the operators telephone circuit OT to the talking conductors as hereinbefore described in connection with an inward call. After ascertaining that a connection requiring the attention of the through operator at the distant ofiice is required the operator actuates through key 00 and inserts plug I into jack 2. Relays 4 and 5 function as hereinbefore described and likewise do relays 6, l and I I with lamp 8i and associated resistances 83 and I00. The actuation of key 50 operates relay I6 over a circuit traceable from ground on key 60, through winding of relay It to battery on the right-hand normally closed contacts of relay 88. Relay I6 locks to ground through its left-hand inner contacts, disconnects battery on its righthand contacts from the winding of relay I! and operates relay 88 through a circuit that may be traced from battery through the left-hand outer contacts of relay It, winding of relay 83, lower iiiner operated make contacts of relay l, over ring conductors of plug I and jack 2, lower winding of retardation coil SI, left-hand winding of relay 25, left-hand normally closed contacts of relay 23 to ground. Relay 88 in operating locks to battery on its right-hand inner make contacts, disconnects from battery on its right-hand normally closed contacts the winding of relay I5 which releases and also disconnects at its left-hand contacts conductor Hi from conductor 29 thereby separating temporarily the ring conductors of the two ends of the cord circuit TC to avoid the possible shunting effect from the calling line. Relay 25 also operates in the circuit hereinbefore traced for the operation of relay 88 and operates relay 9? connecting thereby source 30 of 1400/20 cycle current to the toll line as hereinbefore described. When relay I0 releases it disconnects battery at its left-hand outer contacts from the winding of relay 88 and reconnects battery on its right-hand normally closed contacts to the winding of relay I'I, thereby operating relays l1, I8 and 20 over the circuit hereinbefore traced in connection with the description of an inward call. Relays 2i and ill and busy'signal 28 also operate. The 1400/20 cycle current passing over the toll line operates relay 5i of receiving circuit RC2 at the distant toll office which causes 1000/30 cycle current to be sent back to the originating end as hereinbefore described to operate relay 6'! of receiving circuit RC9. Relay 61 operates relay 23 which opens at its left-hand normally closed contacts the operating circuit of relay 25, and the holding circuit of relay 8? hereinbefore traced. Relay 82 releases, reconnecting conductors 29 and SI. Relay 25 also releases, releasing relay 91, disconnecting thereby the source 30 or,1400/20 cycle current from the toll'line and causing the release of relay M at the terminating end. Relay 5I in releasing, releases relays 54 and 55. Relay 55 in I releasing opens the operating circuit for slow operate relay'li'l, before it has had sunicient time to operate and. also closes a circuit for operating relay "I2 which is traced from ground on the normally closed upper contacts of relay II through lower winding of relay l2, right-hand inner back contacts of relay 55, operated contacts of relay '55 and right-hand normally closed contacts of relay ":IE to battery. Relay 12 in operating closes a circuit for lighting lamp of through cord circuit THC which may be traced from battery through the upper inner operated contacts of re lay l2, lower normally closed contacts of relay S t and lamp 06 to ground. In response to this signal, telephone circuit OTI is connected by circuit means not shown to conductors I9 and 80, thereby enabling the through toll operator to obtain information for completing the connection. When this is obtained, plug 95 is inserted in the jack of the circuit (not shown) leading to the line of the called subscriber. Relay 94 now operates through a circuit traced from battery through the winding of relay 9t, lower inner operated contacts of relay I2 to ground on the sleeve conductors of plug 95 and said jack hereinbefore mentioned. Relay 94 in operating opens the circuit at its lower normally closed contacts through lamp 0t, hereinbefore traced, extinguishing said lamp and also connects through its make contacts conductors 19 and 80 to the tip and ring conductors of plug 95. Relay I? also locks through its upper outer make contacts to ground on the lefthand normally closed contacts of relay I6 and disconnects ground at its lower normally closed contacts from the windings of relay II. The connection to the line of the called subscriber is now completed over circuits not shown and which are not a part of this invention.

After the subscribersdisconnect, in response to the disconnect signals at the originating end (Fig. 1) all apparatus thereat is restored to normal as explained in connection with the description for a call to the inward'operator. At the completing end (Fig. 2) relay l2 releases, releasing relay 94, when release relay "I6 functions and all other relays are restored to normal as explained hereinbefore in connection with the description for an inward call.

What is claimed is:

1. In a signaling system, an outward operators position, a line extending therefrom and terminating at a plurality of diiierent operators positions, line signals at each of said distant posi tions, a source of alternating signaling current at each end of'the line, means at the outward position for connecting its associated source of current to the line as a connect signal, means at the other end of the line responsive to said transmitted connect signal to operate the line signal at one of said positions and to connect the signal current source thereat to the line as an answer-hack signal, means at the outward position responsive to said answer-hack signal to disconnect said connect signal current from the line, and operator controlled means at the outward position adapted to accelerate disconnection of the connect signal in response to the answerback signal whereby the connect signal is shortened, and means at the distant end of the line responsive to said shorter connect signal impulse to prevent the line signal from operating at said one position and to operate the line signal at the other position.

2. In a voice frequency signaling system, a line, an outward operators position at one end of the line, two different positions at the other end of the line, an operators connecting circuit and a source of alternating current at the outward position, a line signal at each of the different positions at the other end of the line, and means for connecting said current source to the line responsive to association of said connecting circuit with the line, means at the other end of the line responsive to said line current for operating a predetermined one of said line signals and for causing disconnection of said source at the outward position, selective means at the outward position for accelerating the disconnection of said source by a predetermined length of time, and means at the other end of the line responsive to a predetermined shorter duration of the line current to prevent operation of the first line signal and to cause operation of the other line signal.

3. In a signaling system, a transmitting station, a receiving station, a line interconnecting said stations, a source of alternating signaling current of a predetermined characteristic at the transmitting station, a source of alternating signaling current of a different characteristic at the receiving station, a plurality of signals at the receiving station, means at the receiving station responsive to the connection to the line at the transmitting station of said signal current to cause the connection to the line at the receiving station of the associated source of signaling current thereat and to cause the operation of a predetermined one of said signals and to prevent the operation of the other of said signals, means at the transmitting station responsive to the connection to the line at the receiving station of the source of signaling current thereat to cause the disconnection of the source of signaling current at the transmitting station, means at the receiving station responsive to the disconnection of signaling current at the transmitting station to cause the disconnection of the signaling current at the receiving station, and means at the transmitting station for accelerating the disconnection of the source of signaling current thereat whereby the second mentioned of said signals is operated, and the operation of the first mentioned signal is prevented.

4. In a signaling system, a line, an operator's position and a connecting circuit at the outward end of the line, two different operators positions at the inward end of the line, a source of alternating signaling current at the outward end of the line of a certain characteristic, a source of alternating signaling current of a different characteristic at the inward end of the line, line signals at each of the positions at the inward end of the line, a receiving circuit at the outward end of the line, a receiving circuit at the inward end of the line, means responsive to the association of said connecting circuit with the line for connecting to the line at the outward end said source of signaling current thereat whereby said receiving circuit at the inward end is caused to function, means at the inward end responsive to the functioning of the receiving circuit thereat whereby the said source of signaling current at the inward end is connected to the line thereat and a predetermined one of said line signals is caused to operate, the operation of the other of said line signals is prevented and the receiving circuit at the outward end is caused to function, means at the outward end of the line responsive to the functioning of the receiving circuit thereat to cause the disconnection of the signaling current at said outward end, means at the inward end responsive to the disconnection of said signaling current at the outward end to cause the disconnection of said signaling current at the inward end, operator controlled means at the outward end for accelerating the disconnection of said signaling current thereat in response to the connection of said signaling current at the inward end to prevent the operation of the first mentioned line signal and to operate the second mentioned line signal.

5. In a voice frequency signaling system, a line, an operators position and connecting circuit at the outward end of the line, two different operators positions at the inward end of the line, a source of modulated voice frequency signaling current at the outward end of the line of a certain characteristic, a source of modulated voice frequency signaling current of a different characteristic at the inward end of the line, a line signal at each of said two positions at the inward end of the line, receiving circuits at the outward and inward ends of the line each tuned to detect and amplify modulated voice frequency signaling current of a predetermined characteristic incoming over the line, means for connecting to the line at the outward end said source of modulated voice frequency signaling current thereat responsive to the association of said connecting circuit with the line whereby said receiving circuit at the inward end is caused to function, means responsive to the functioning of said receiving circuit at the inward end whereby said source of voice signaling current thereat is connected to the line, the receiving circuit at the outward end is caused to function, and a predetermined one of said line signals is operated and the operation of the other signal is prevented, means responsive to the functioning of the receiving circuit at the outward end whereby said source of voice frequency signaling current thereat is disconnected, means at the inward end responsive to the said disconnection of the voice frequency current at the outward end, whereby the voice frequency current at the inward end is disconnected, and operator controlled means at the outward end whereby the disconnection of the voice frequency signaling current thereat is accelerated, and means at the inward end whereby said accelerated disconnection of the voice frequency current at the outward end causes the operation of said second mentioned signal and prevents the operation of said first mentioned signal.

JOHN MESZAR.

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