Patent GB-794817-A (GB)
Title: Improvements in or relating to automatic telecommunication exchanges
Inventor: HARTLEY GEORGE CLIFFORD
IPC: H04Q3/00
Filed: 1956-07-13
Abstract: 794,817. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. July 13, 1956, No. 21799/56. Addition to 794,820. Class 40 (4). In an automatic exchange as claimed in the parent Specification, the first of the odd number of stages of co-ordinate multi-switches includes a number of sets of multiswitches, each set handling a different type of traffic (e.g. originating traffic, incoming traffic), the last stage includes a number of sets of multi-switches, each set handling a different type of traffic (e.g. terminating traffic, outgoing traffic), and the common test equipment controls the establishment of every available type of connection through the odd number of stages of multi-switches. The embodiment shown in Fig. 2 caters for local-to-local, local-to-outgoing, and incoming-to-local calls and to this end the first stage of multiswitches (the A frame) includes a set of switches LA1 to LA50, the inlets of which are connected to first links and which handles locally originated traffic, and a set IA1 to IA50, the inlets of which are connected to incoming links accessible from incoming junctions and which handles incoming traffic. The B frame has three sets of switches, AB1 to AB10 handling local-to-local traffic, OB1 to OB10 local-to-outgoing, and IB1 to IB10 incoming-tolocal; and the C frame two sets, LC1 to LC50 handling terminating traffic, and OC1 to OC50 outgoing. The route selector (Figs. 4A, 4B) operates in substantially the same way as that of the parent Specification, but comprises in effect three separate path selectors for local-tolocal, local-to-outgoing, and incoming-to-local calls, respectively in each of which a free path is chosen from among those available, not arbitrarily by a lock-out arrangement as in the parent Specification, but by pulsing the ten " path gates " such as gate G1 (Fig. 4A) of each path selector singly and successively by pulses P1 to P10, respectively, the first available path being thus chosen. A further embodiment is described (Figs. 5-10, not shown) which also caters for incoming-to-outgoing traffic by the provision of a second group of outlets on the IA switches giving access to a fourth set of B frame switches and thence to a second group of inlets of the 00 switches. In addition provision is made of overflow routes by an additional (third) group of outlets on the LA switches giving access via the first group of inlets of a fifth set of B frame switches to a third group of inlets of either the LC switches or of the OC switches, and an additional (third) group of outlets on the IA switches giving access via the second group of inlets of the same B frame switches to the same LC or OC inlets. The route selector of this embodiment has in addition to the three path selectors of Fig. 4A, 4B a fourth similar path selector for incoming-to-outgoing paths and a fifth overflow path selector which tests overflow paths for all types of traffic and the " path gates " of which are tested by pulses P11 to P20 so as to be effective in choosing a path only if no direct path (tested by PI to P10) is available.