Patent GB-416851-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1933-03-16
Abstract: 416,851. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, TAYLOR, R., 30, Oulton Road, Wavertree, both in Liverpool, and BAKER, G. T., Blackbrook, Caerphilly, Glamorgan. March 16, 1933, No. 8027. [Class 40 (iv).] Calls from a rural office to the automatic apparatus at a main exchange and to a manual board at this exchange are routed over the same group of junctions in response to digits 9, 0, respectively, the rural office selector in response to digit 9 being adapted to step automatically to the tenth level and to transmit forward a discriminating signal which controls switchover at the main exchange. Further discriminating signals may also be transmitted when the calling rural-office subscriber is at a paystation. The rural-office selector serves as a P.B.X. final selector for local calls which are denoted by a first digit 2 or 3, the selector dropping back in response to this digit which also effects wiper-selection. Direct junctions to adjacent manual and automatic rural offices are connected to levels 5-8 and if a direct junction is found the second digit is absorbed, but if no direct-junction is available, the selector moves automatically to its tenth level to select a junction to the main exchange at which the second digit is then effective to route the call to the wanted office. Finder arrangements. The rural office may contain from 50 to 200 lines. With 50 lines, six finders associated with a common control circuit and each linked to a final selector are provided, and for 100 lines this arrangement is duplicated. For more than 100 lines, secondary finders are introduced, there being twelve arranged in a single group and each linked to a final selector, whilst a separate group of six primary finders is allotted to each group of fifty lines. The detailed circuit arrangements, Figs. 6, 7, 10, show both primary and secondary finders, but if only primary finders are employed, they will be connected directly to the terminal assembly at the left of Fig. 7, and strap 30, Fig. 10, will be inserted. When a subscriber, Fig. 5, calls, line relay L completes a circuit over conductor STG1, from earth on lead 12, Figs. 5, 7, provided at least one link circuit is free, for group start relay 2SA, Fig. 12. Starting circuits over leads STD1, STD2 are thus completed for two allotters each giving access to all the primary finders in all groups and each serving to allot an idle finder in the group required owing to the marking in bank T1 of certain contacts in accordance with the arrangement shown in Fig. 12. Two finders of the same group, each associated with a different allotter thus hunt simultaneously, but if calls in two groups occur simultaneously, relay 2SK operates and switches over the connections so that each allotter controls a single finder in one of the groups. In the allotter shown, Fig. 6, earth on lead STD1 completes a circuit for relay G which interacts with magnet FDM until a primary finder is reached in which battery is present on wiper T1 and earth is absent from wiper T2. Relay H then operates completing a start circuit ST1 for the secondary allotters, Fig. 10, and causing the magnet LFM of the selected primary finder to interact with relay G until the calling line is reached when SH operates. In the two secondary allotters, relays SA, 1SB operate and cause two secondary finders to hunt simultaneously similarly to the primary finders, the primary finder in use being marked over lead S. When this is found relays HF, 1SH operate completing a circuit for relay HA in the link circuit which in turn operates RT. Final selector ; local call. Impulses are repeated by relay A to vertical magnet VM in parallel with relay C. A first digit 2 or 3 denoting a local call causes the operation of relay LO with or without wiper-switching relay WS. On the relapse of C, relay LO closes a circuit over off-normal contacts N1 for release magnet ZM and when release is complete, DA operates. At the end of the next (tens) digit which is repeated to magnet VM, relay E operates over contacts N1 and completes a circuit for relay MS which changes over the circuits of relay D, I, Fig. 7, to provide a local feed. The units digit is repeated to rotary magnet RM, the closure of rotary-off-normal springs NR4 operating relay NS. At the end of the digit, between the relapse of relays C, E, 2G operates and test relay 1H is connected up. If the called line is busy and is an individual line, relay HS operates over bank PBX and connects up busy tone and flash BF. If the first line of a P.B.X. is found busy, relay 2G interacts with rotary magnet RM until a free line or the last line of the group is reached. When a free line is found, relay 1H operates completing an interrupter circuit for ringing relay F, and when the called subscriber replies, relays D, I operate and release RT. Call to manual position at main exchange. If digit 0 is dialled, vertical wiper VW completes a circuit on the tenth level for operating relays MS, NS in series. On the relapse of C the rotary magnet interacts with relay 2G to select an idle junction to the main exchange when relay 1H operates. Battery on the positive wire energizes relays 1A, OC, Fig. 13, and relays 1B, MC operate and switch the junction over to the manual position, Fig. 14, at which LB operates and lights calling lamp CLP. When the operator plugs in, sleeve relay S short-circuits one winding of LB so that relay I, Fig. 7, is able to energize and by releasing RT complete the circuit over the negative wire for relay LA. When the called party replies, relay 1D short-circuits a winding of LA causing the operation of D, Fig. 7. When the calling party hangs up, relays A, B release, but C energizes to withhold the releasing shunt from relay HA so that release only takes place when the operator clears, Call to automatic equipment at main exchange. When digit 9 is dialled, wiper VW completes no circuits, but on the relapse of C relay VC operates completing a circuit for operating the vertical magnet VM to step the wipers to the tenth level at which NS operates and VC is released. Selection of an idle junction occurs as before, but since MS is not energized, relays I, D are looped across the junction and differential relay OC does not operate. Relay 1A completes a loop for the automatic apparatus and on the first impulse of the next digit relay 2H operates to switch the junction circuit through metallically to the first selector. Metering. In a non-local call, the second digit dialled is repeated over lead 26, Fig. 11, to a zone-determining switch which subsequently transmits over lead 27 the correct number of metering impulses, a rectifier MRC2 ensuring the release of the meter after each pulse. Metering of local calls is effected similarly, a single impulse being transmitted over lead 27. Off-normal springs of the zone-determining switch may be connected in lead 15 to ensure that the link is non-selectable until the switch has completely restored. Call from paystation. Paystations are characterized by a high-resistance battery connection Y2, Fig. 5, causing the operation of a relay CB when NS energizes on a call from such a station to the manual operator. When the junction is switched over to the operator's circuit, Fig. 14, relay LA energizes over contacts cb6, i4, at the same time as LB to flicker lamp CLP. If, on an automatic call, the first two digits dialled denote a number requiring an excess fee, the zone-determining switch operates relay CB over lead 28. CB releases RT and a circuit is completed for release magnet ZM. Relays RT, VC then operate and vertical magnet VM interacts with relay 2G to raise the wipers again to the tenth level in which a connection is extended to the manual position and lamp CLP flickered as before. Call to adjacent rural office ; alternative routing. A first digit 7 or 8 causes the operation of relay NS over a common lead similar to lead 13, Fig. 5, provided at least one direct junction is idle. Hunting occurs as before and the second digit, which is not required in a directly-routed call, is absorbed since contact a2 is shunted by a circuit comprising postsprings NP and contacts da3. During this digit relay E operates so that on the relapse of C, DA energizes to open the shunt. If no direct junction is available, NS does not operate, VC is energized, and the selector is stepped to the tenth level and the call routed via the main exchange at which the second digit, not now absorbed because springs NP open on the tenth level, serves to route the call to the wanted rural office. A first digit 5 or 6 denoting a manual rural office produces similar effects with the exception that both relays MS, NS are energized and manual calling conditions are established. Delayed dialling. The same relays MA, MB employed for delayed metering are also employed to control release in the case of delayed dialling, the circuits being switched over from one pair of cams St, Zt, to a second set Sm, Zm, when rotary off-normal contacts NR3 change over. If delay occurs in dialling the operation of MB releases HA and the connection. Delayed release. Relay P, Fig. 5, operated by K remains locked over the loop if the calling party fails to release to lock the party out of circuit. Call from manual exchange. Lines from manual exchanges transmitting battery impulses over the a-wire have the fourth terminal D connected to battery over a low-resistance Y1 Fig. 5, so that relay BD operates connecting earthed relay IL, Fig. 7, to the a-wire, and suitably changing over the impulsing circuits, Fig. 11.