Patent GB-341524-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1929-10-17
Abstract: 341,524. Automatic exchange systems. AUTOMATIC TELEPHONE MANUFACTURING CO., Ltd., Strowger Works, TAYLOR, R., 30, Oulton Road, Wavertree, and COMYN, F. E., 12, Rawlins Street, Fairfield, all in Liverpool. Oct. 17, 1929, No. 31585. [Class 40 (iv).] Bi-directional call-finders hunting freely in both directions of motion are controlled by common relays associated with an allotting switch. Two arrangements are described, the second of which comprises call-finders having two sets of wipers. The vertical bank-marking arrangement is not shown in full but may be as described in Specification 293,294, [Class 40 (iv), Telephones &c.], and the grouping and emergency arrangements described in that Specification may also be used. First arrangement, Fig. 1. When a call is initiated ground connected to a contact in the vertical marking bank VB operates A and the consequent energization of K over a1, kr1, DM, connects FR to the outgoing negative conductor so that the line relay at the first group selector operates and ground is returned over the release wire P<1>. Also, C and G pull up in series over wipers 16, 15 of the allotter and interrupter springs V, R of the vertical and rotary magnets. Relay C removes the short-circuit about FR which completes the circuit (VM, rotary off-normal springs RN, c3, g1, fr3) of the vertical magnet which interacts with G to step the call-finder until ground over VB holds G over R, k3. Relay C holds during the stepping but is short-circuited over VB when the calling level is found and falls back to change over to the rotary magnet and prepare a circuit for KR which, however, is short-circuited over g3. The wipers are rotated out of marking bank VB and G holds over k3, R, V, c2, g2, fr5, until it is released at R. Relay KR pulls up to prepare the circuit kr3, 14, RN of switching relay H, and G is reoperated by ground on non-calling lines over P, h2, R so that it interacts with RM until the calling line is found and the short-circuit over relay H is removed. Relay H operates over G, k3, R and the previously traced circuit, but G remains inert. H locks up, in series with VM, to ground returned from the group selector, releases FR and extends ground on P<1> back to the cut-off relay of calling line. The relapse of the line relay is followed by that of A, and the release of FR releases KR and K which connects ground from off-normal springs N2 to magnet DM to step the allotter. When the connection is released, the switching relay at the group selector falls back to complete a circuit over Z for release magnet ZM. Second arrangement, Fig. 2. When a call is initiated, relays A and K energize as before ; but G is a shunt field relay and C operates in series with G(ii) and connects up G(i) to energize this relay. The circuit of G(ii) is adapted to be opened by V so that VM and G interact until the calling level is reached and G(ii) remains held over VB. Changeover relay C falls back, FR pulls up, and RM steps the switch out of VB, G remaining held over g4, G(i) and g2, G(ii) until the circuit of G(ii) is opened at R. KR pulls up as before to prepare the circuits of the switching relays HA, HB. Magnet RM and relay G interact for rotary hunting, the two windings of G being connected respectively to wipers P1, P2. Hunting continues so long as ground on non-calling lines is encountered by both P1 and P2. When a calling line is reached by P1, G does not re-operate, and HA, being no longer short-circuited, pulls up over kr3, RN, HA, R, G(i), holds to ground on P1, opens the circuit of HB, and extends ground back to wiper P1 with results as previously described.