Patent GB-1193075-A (GB)
Title: Improvements in or relating to Automatic Telephone Systems.
Inventor: CORNER ARTHUR CHARLES
IPC: H04Q3/00
Filed: 1966-09-02
Abstract: 1,193,075. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. 31 Aug., 1967 [2 Sept., 1966], No. 39444/66. Heading H4K. Groups of outgoing relay sets have access to a group of senders, each group of relay sets having access to a particular sender as first choice and having access as second choice to a sender which is first choice of another group, an overflow sender or group of senders being available to all groups as third choice. The cross-bar transit exchange of Fig. 1 has first stage routers 1SR(1)-1SR(4), only one being shown, and two second stage routers 2SR(1), 2SR(2), only one being shown. Registers A serve both-way relay sets BWRS which receive and send in multi-frequency code. Registers B serve incoming relay sets IRS which receive loop disconnect pulses and send multi-frequency code. Either type of register has access to routing controls RCX, RCY, for X or Y type paths across the exchange. Second stage routers 2SR(1), 2SR(2), provide paths between the incoming relay sets IRS and the relay sets BWRS used as outgoing junctions. Both sets IRS and the sets BWRS, used as incoming junctions, have access directly over the first stage routers 1SR(1)-1SR(4) to blocks of outgoing relay sets AOGRS, BOGRS. Each block has a sender allotter SA1, SA2, and a group of senders SDR. The groups of outgoing relay sets in each block are selected by any one of four markers; LMX, LMY, in each second stage router. The senders SDR receive multi-frequency code and send loop disconnect impulses, The sender allotting circuits are shown in Figs. 5 and 6 which suppose that the outgoing relay sets of a block are divided into ten groups G1-G10 of ten relay sets each. Of the ten relay sets OGRS1-OGRS10 of a group only one, OGRS1, is shown. Each group has a relay set identifier RSI1-RSI10, of which only RSI1 is shown. The block of relay set groups is served by a group identifier JGI and group selection is made by any one of four markers one of which is shown at LM. The senders SDR1-SDR10, if free, each mark a relay MA in the relay set group for which they are first choice and mark a relay MB in the relay set for which they are second choice. The sender SDR11, if free, provides a mark for relays MC in all groups. Supposing all senders are free, the relays MA are operated in all group identifier circuits such as RSI1. MA operated, as illustrated, disables the operating path for MB and MC. If only the second choice sender is free the relay MB will operate and this disables MA and MC. Thus if the second choice sender is nominated by MB the subsequent freeing of the first choice sender does not upset the nomination of second choice. Calls in demand of a sender may arrive from any one of the four first stage routers ISR(1)-1SR- (4) and concurrent such demands are limited to one at a time by a circuit ESC1 in the marker which signals the relay set groups over parallel sets of contacts MA, MB, MC. If none of these contacts is made the associated relay set group has no senders available and is not available. Each available group operates a relay LC to connect a test path to each relay set of the group. The wanted group is indicated from a circuit GR in the marker and connects earth over the LC contacts of that group, free relay sets in which respond by operating their T relay. Marks are thereby reverted by contacts of T on all M-wires of free relay sets in the wanted group, the exchange selecting one of the routes so indicated by the process known as "self-steering" and operating the relay K over the P-wire of the selected relay set. Since there are four markers LM the senders are allotted one at a time and a circuit ESC 2 ensures that of relay sets concurrently seized within a group only one is dealt with at any given time. Contacts D1-D10 extend the MA, MB, MC, relay conditions to the individual relay sets of the group including the selected one where a relay SA, SB, or SC, operates accordingly to connect the relay set to the nominated choice of sender. Before this, however, contacts D1-D10 also seek the advice of a circuit ESC 3 in a group identifier JGI which ensures that of concurrent demands for a sender arising in different groups only one is dealt with at a time. If ESC3 so indicates, and the group has a sender available, a relay MK operates to forward the MA, MB, MC, relay states to the seized relay set of the group. Whichever of the SA, SB or SC relays respond in the relay set the corresponding sender is signalled and replies by operating relay SS in the relay set. At this stage the sender is coupled between inlet RSB and outlet OG of the relay set and transmits as loop disconnect pulses digits received from the register as multi-frequency codes. When transmission is complete contacts SR operate to release the sender seizing relay SA, SB, or SC, which releases the sender. Relay SS also releases to provide a direct path out over the relay set.