Patent GB-809870-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: GALVIN JOHN LESLIE
IPC: H04Q3/00
Filed: 1956-09-07
Abstract: 809,870. Automatic exchange systems. AUTOMATIC TELEPHONES & ELECTRIC CO. Ltd. Aug. 14, 1957 [Sept. 7, 1956], No. 27402/56. Class 40 (4). In a trunk exchange having a rank of group selectors each giving access to a number of groups of outgoing trunks arrangements are provided whereby selectors requiring access to busy groups are formed into separate queues  appropriate to the groups and each time a trunk in a busy group becomes idle the selector at the head of the relevant queue is released therefrom to search for the idle trunk. As described the selectors are motor-driven uniselectors with staggered wipers adapted for 4-wire switching and controlled by marking from a digit switch. A uniselector is described with reference to Figs. 1-8, but only Figs. 6, 7 which show the digit switch DS (except for its marking bank) and a queue finder QF are illustrated here. The queue control circuit is shown in Figs. 10, 11. If the required group lies in the second half of the uniselector bank, as soon as the digit switch has advanced sufficiently to determine this a circuit made over wiper DS8 for relay PP (not shown) to bring about a pre-positioning of the uniselector to the end of the first half of its bank in order to reduce hunting time. For groups of trunks which require storage and regeneration of the succeeding digits the RG terminal connected to bank DS7 is strapped to earthed terminal ET in order, after the dialling relay has fallen back, to take into use an idle impulse regenerator by means of relay RG (not shown). If no regenerator is available a busy signal is given. The incoming digits are followed by an end-ofdialling signal which is repeated forward after the regenerated digits. Call entering queue. In the case of a busy group, relay AGB associated with that group is up and earth on the TGB terminal energizes relay GB over wiper DS4. If the group is one leading to an automatic exchange but not normally requiring the use of a regenerator the RG terminal is strapped to terminal AT which is earthed by the operation of GB so that a regenerator is taken into use in this case. Relay GB prevents movement of the uniselector, starts the queue finder QF and returns a signal to indicate delay in the setting up of the call. A total of 48 queue positions are provided which may be allocated to the trunk groups as required by connections between bank DS2 and banks QF5, QF6 via terminals TQM and TQK. Banks QF3,QF4 are connected over - terminals TQ to queue relays QA, QB ... and terminals Q in the queue control circuit, the queue relays controlling lamps LP. The Q, A, L, G terminals are connected to terminals ST, FN, CQ as shown for the first and second groups, to mark the first and last of the queue positions allocated to each group. As shown, positions 45 ... 49 of the queue finders are allocated to the first group, and on a call to that group the first relay TQM (not shown) of the queue finder QF is connected in succession to queue relays QE ... QA. The queue relays are of high resistance, and, assuming that the queue is empty, the test relay does not operate until it is connected to QA which is normally shunted by resistance R41 over terminal ST1. Finder QF thus stops in the first queue position, while QA lights lamp LP1 and shunts QB by resistance R21 so that a second selector requiring the same group takes the second position in the queue, and so on. Release of call from queue. On a trunk becoming idle, relay AGB is released by earth on wire GBL and shunt resistance R41 is disconnected, so that QA falls back and the queue finder QF standing in position 49 advances to 50, in which a circuit is made to start the uniselector in search of the idle trunk. QA removes the shunt from QB and the queue finder second in the queue steps to position 49 in which QA re-operates, since R41 has been replaced by the release of AGC. If there are any more calls in the queue, the relevant queue finders step on in turn. When the idle trunk is seized, earth is removed from wire GBL and relays AGB, AGC re-operate. It will be noted that while AGB is back, the group busy, earth on TGB is maintained as long as any of the queue relays are up. If several trunks, become idle simultaneously, however, earth remains on GBL after one has been seized, and in this case AGD falls back after a 2-second intervat and causes the sequential re-operation and relapse of AGB, AGC to release the call then at the head of the queue, this action being repeated if necessary. Queue full. The last queue relay QE pertaining to the group operates FN which controls statistical meters. If a call for the busy group is made at this time, QF goes to position 50 and the uniselector hunts without effect and stops in a position from which a busy signal is returned. Delay working. Actuation at the local manual board of the delay key pertaining to a trunk group operates relay ADL which earths wire TDL instead of TGB. When a call for this group is received, relay DL (not shown) energizes over bank DS4 and marks outlets of the uniselector leading to delay circuits. The succeeding digits are registered in a regenerator, and the end-of-dialling signal starts the uniselector which switches through to a delay operator who may book the call and set it up in due course. Alternatively she may return a signal which causes homing of the uniselector, whereupon DL goes back and the call enters the queue. A busy signal is given if no delay circuit is available. Direct calls to manual exchanges. These are dealt with in the same way, but since digit storage is never required the relevant RG terminals are left disconnected.