Patent GB-370086-A (GB)
Title: Improvements in and relating to telephone exchange systems
IPC: H04Q3/00
Filed: 1931-01-27
Abstract: 370,086. Semi-automatic exchange systems. SOC. NOUVELLE DE CONSTRUCTIONS TELEPHONIQUES BREVETS TCHOUBRITCH-DERVAL, 38, Rue du Chateau des Rentiers, Paris. Jan. 27, 1931, No. 2692. Convention date, Jan. 31, 1930. [Class 40 (iv).] A network comprises a number of local - battery offices CR connections in and between which are controlled by an operator at a main office MA. Each of the subordinate offices comprises one or more local talking circuits shown in dotted lines and an appropriate number of two-way junctions leading towards and away from the main office. Each junction is provided at the end remote from the main office with a two-digit register marker of relay type. In the Figures, Roman numerals adjacent to unconnected leads terminating in circles designated by Arabic numerals indicate the numbers of the Figures in which the continuations of these leads are to be found. In the system described, the initiation of a call by the operation by a subscriber of his magneto or the arrival of a call from an office more remote from the main office starts a relay call finder common to the whole office which connects the calling line or junction to the first idle junction towards the main office. The operator on observing the lamps 77, Fig. 13, rings the calling junction and thus the calling line and the calling party then removes his receiver. The operator then connects the nearer party (calling or called) to the common local circuit at his office and then calls the more remote party with the aid of one or more of the individual register markers and connects him to this circuit. In the system described in detail the offices are assumed to have only one local circuit. Calls through the main office are extended manually in known manner. Calling controlling operator. When the calling subscriber operates his magneto, his relay D, Fig. 6, locks up in series with the common relay B, Fig. 7, which energizes Z1, Fig. 11, over back contacts of relays J, M<1>, M, provided there is an idle junction outgoing towards the control office. Z1 energizes Z2 and is thus released whereupon Z2 falls and Z1 pulls up again. The first operation of Z2 energizes the first of the relays Y of which there is one for each subscriber's line and one for each junction incoming from the side remote from the control office. Y1 locks up and arranges for the operation of Y2 on the relapse of Z2. Y2 locks itself and unlocks Y1 and when Z2 pulls up again Y3 is operated, and so on. When the relay corresponding to the calling line is operated, circuits are made over c1, c2, c3 and contacts of the operated D relay for the connecting relay C of that line corresponding to the first idle junction, the circuit involving contacts of relays M1, J1 of the first junction and if that junction is busy the corresponding contacts of one or more of the relays M2, M3, J2, J3, &c. Relays B, D and the call-finder set, Fig. 11, are then released. Assuming the second to be the first idle junction C2 locks in series with J2 which energizes L2 to connect battery from 28 to the left-hand talking wire. As a result V in the incoming junction circuit, Fig. 4, at the next office (if any) is energized in series with B, and the call-finder set there ultimately puts battery on the wires 161, 162, 163 causing the calling junction to be connected to the first idle outgoing junction by one of the relays N which acts similarly to the relay C which connected the calling line to the junction at the previous office. The relay N (say N1) locks in series with M1. Battery is thus extended over 168 to the next office to cause similar operation if it is a rural office or if it is the main office to light the calling lamp 77, Fig. 13. Reply by controlling operator. The operator on plugging in connects battery to the righthand junction wire energizing P, Fig. 4, at the tandem office. P energizes S which energizes T. A holding circuit is thus made for N1. She then rings the line and when the calling party removes his receiver, K2 shunts condenser 79 energizing the bridged relay SP1 in the cord circuit whereupon SU goes out and the operator ascertains the number required. Establishing local connection. When the listening key is thrown, battery over 81 and the right-hand junction wire is connected to a, Fig. 8, which energizes b, e, c. The operator then depresses and releases BL, causing with the aid of RG, RR the transmission of two single impulses. These control the register marker shown in Figs. 8, 9 and 10 and described in detail in a later paragraph, and result in the operation of S1, Fig. 9, H2, Fig. 7. The latter connects the local circuit to the junction and energizes A to connect the subscriber to the local circuit and K2 then falls back. She then dials the wanted number and rings the line. The register marker operates the appropriate relay C and when the called party replies K2 pulls up again. Apprised of this by the extinction of SU the operator again operates BL to energize H2 and the called subscriber's relay A connects him to the local circuit. The operator then withdraws the plug releasing the junction and relays C. At the tandem office (if any) P falls shunting S which after a brief interval shunts T. In the interval between the relapse of S and T, M1, N1 are released. While either subscriber has his receiver off, F, Fig. 7, is operated and holds the relays A. When both hang 'up, F is released and frees the relays A, battery being kept off the holding wire temporarily by G. Inter-office calls. The operator connects the nearer party to his local circuit and then dials the number characterizing in the nearer office one of the junctions leading in the direction of the more remote office. As a result, one of the relays N connects the two junctions together and the operator then controls a register marker in the remote office to ring up the subscriber there or to get connection with a further junction. When he replies, shunting the condenser such as 79, the battery connected at the manual office is extended to the relay U, Fig. 4 (P, S, T being already operated), which energizes O to connect the junction from the remote office to the local circuit at the nearer office. O energizes Q, R and unlocks M1, N1 whereupon P, S, T fall back. W, X pull up over the loop from the more remote office. When the more remote subscriber hangs up, W falls but X is held over 25 in series with a at the outgoing end of the junction and a circuit is made for E, Fig. 7, which unlocks relay A of the nearer subscriber. Busy signalling. When the operator dials the number of a busy junction, say LO14, T being energized, the relay I of the incoming junction is operated and connects the junction to the buzzer 203. Operation of register markers, Figs. 8, 9 and 10. When the speaking key is thrown, a, b, e and c, Fig. 8, are operated. a and b repeat the dialled impulses. The first impulse energizes d, f and g and the first counting relay i, Fig. 10, at the beginning and releases c at the end. The next impulse releases d to energize the second counting relay (which releases the first) at the beginning and re-energizes c at the end so that the third energizes d and the third relay and so on. At the end of the digit, f is shortcircuited for a comparatively long period and energizes h and the selected tens relay S. At the beginning of the new digit g falls back, and at the end f falls back and makes the marking circuit and shortly afterwards h falls back, breaks the marking circuit and unlocks the tens relays. Wayside station. Having observed by the conditions of the device z that the junction is idle, the user actuates his magneto. The drop indicator AS at the main office responds and the operator there sends ringing current over one line wire and earth by means of a special push (not shown), actuating the indicator AA at the wayside station, and ringing the bell. Relays a, b, e at the adjacent rural office mark the junction busy, e operating in the same way as S or M to cut the circuit 22. The drop indicator AA is reset by restoring the handset. While the junction is busy, the indicator disconnects the magneto at Cr. The magneto at CM disconnects the drop indicator. Listening in and breaking down connection in favour of priority calls. To listen in the operator dials 11 (or operates BL) or, in the case of interoffice calls, dials the number of the nearer of the junctions used to operate one of the relays H and so connect herself to the local circuit. To break down an existing connection she operates one cf the relays C of the party wanted in the pricrity call and then dials 12 to energize E which unlocks both relays A. Emergency working. If, owing to a fault, relays L, K cannot pull up calls are received at the small office on emergency apparatus (not shown) connected to the points Sec. Calls to the manual office are indicated by the drop indicator AS. Re-charging rural. batteries from main office. The voltage of the battery of each office can be ascertained by pressing push u when answering a call. If it is necessary to re-charge, the operator dials 13 to energize v, Fig. 4, which locks temporarily and connects x to the righthand junction wire the other end of which is connected to the ordinary exchange battery so that x being in effect short-circuited does not respond. The plug is then replaced by a special charging plug connected to a battery of higher voltage so that x operates and shunts out v. The special plug is shaped so that it allows the top springs 8 to remain in contact so that calls may be received over the junction during charging.