Patent GB-407286-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1933-11-20
Abstract: 407,286. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, London.-(Siemens & Halske Akt.-Ges. ; Siemensstadt, Berlin.) Nov. 20, 1933, No. 32362. [Class 40 (iv).] A digit switch responsive to an extra digit indicative of a particular party on a partyline is associated in common with a number of final selectors and is connected to any one when a call is made to a party-line after the line has been tested and found free. The extra digit may cause the selection of ringing-current of a particular frequency as in the example described below or the transmission of a characteristic code-signal. In the final selector shown, relay C operates on seizure over the incoming c-wire. The tens impulses coming in over the a-wire are repeated by relay A (i) through V (i) to vertical magnet H and at the end of the digit on the relapse of V, relay U (i) operates so that the units impulses pass to rotary magnet D. The opening of rotary off-normal contacts w1 leaves relay U (ii) dependent on relay V and in the interval between the relapse of V and U, relay P tests the called line. If busy, P does not operate and on the relapse of U, busy tone Bes is connected to windings A (ii), Y (iii), and by induction through windings A (i), Y (i and ii) passes to the calling line. If the called line is free and is not a party-line, the operation of P connects an interrupter sec to relay R. At each operation of R, ringing current is applied over Y (i) and when the called party replies, Y operates and energizes V (ii) which cuts off R. When both parties hang up, the release of relays C, V, closes a circuit for rotary magnet D which interacts with relay U (ii) to rotate the wipers to the end of the bank from which release occurs. If the called line is free and is a party-line, two-step relay X (i) operates over an additional final-selector bank mk closing contacts x2, x3, x5, x6. Relay 1R in the common apparatus connects interrupter RU1 to magnet Da of the finder-switch da 1 .. da 5 and when the final selector is reached, 1P operates over wiper da1 in series with winding (ii) of X which now operates fully. Relay J (i) operates over contacts x4, a2, and energizes 1V. At the first impulse of the extra digit the release of J operates 2V and at the end of this and each succeeding impulse the reoperation of J completes a circuit for magnet Dr of switch dr1 .. dr5. During this operation battery is connected over both the outgoing a- and bleads to prevent any party on the line initiating a call. At the end of the digit, between the relapse of relays 2V, 1V, ringing-current of the required frequency is transmitted over wipers dr4, dr5 to the called line. At each substation on the line, an alternating-current relay connects up a frequency-responsive device which at the wanted substation operates to connect up a direct-current bell. When the called party replies, relay 1S (i) operates, releasing 1R and operating S (ii) which switches through and releases X. Magnet Dr operates over bank dr 3 to advance switch dr 1 .. dr 5 to normal.