Patent GB-1148183-A (GB)
Title: Circuit arrangement to control and supervise switching multiples in telephone exchange systems
IPC: H04Q3/00
Filed: 1966-07-08
Abstract: 1,148,183. Automatic exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 8 July, 1966 [15 July, 1965], No. 30760/66. Heading H4K. In an exchange system utilizing a multistage remanent-relay switching network through which paths are selected by means of a route simulating network, the latter consists of two sets of wires which are coupled through rectifiers to the operate and release windings of the relays. During route finding an " offering " current is passed forwardly through one of the wires of the network whereby all possible free relays are marked whereafter an " access " current is passed backwardly through the other wire of the network whereby, in conjunction with a marking of selected ones of the marked relays, a unique set of relays is operated. The initial marking and the correct operation and release of each of the relays is signalled to the common control circuit via the decoupling rectifiers having the prefix G in the drawing. Particular description.-Fig. 3 depicts a 2 x 2 remanent relay switching matrix. Each relay consists of a sealed glass tube having a contact pair at each end and a magnetic, conductive ball which, under the control of an operate winding I and a release winding II, operates one or the other of the two contact pairs. In operation, an " offering " current may arrive over offering wires me 1 and/or me 2, and, provided none of the relays K1-K4 are operative, it is passed on via diodes D9, D10 to the offering wires ma 1 and/or ma 2. Of the various offering wires which may thus be marked at the outlet side of the network one is selected and an " access " current is reverted over its associated access wire da 1 or da 2. At each switching stage the " access " current blocks diodes G5, G4 whereby " offering " current on the wires me 1 or me 2 is passed via reading wires L1, L2 to a control circuit which responds by marking one only of the setting wires E1 or E2. Thus, if da 1 and E1 are marked, relay K1 comes up so as to break the offering wire continuity at contact k12, to disconnect the access wire from this matrix at contact k11 and to through connect it (contact k13) to the preceding stage whereat a similar process occurs and also to switch through the speech path. Correct operation of the crosspoint is indicated by the removal of current from the wire U. In order to release a connection, the relevant access wire is marked as also is the release wire A connected to the first stage of the network. Consequently relay K1 falls back whereby supervisory current again flows through wire U. The A wire in the next stage is then marked and the process is repeated. Overflow.-If an outlet in a wanted direction does not have access to a free junctor an alternative path which includes as many as possible of the already selected crosspoints is determined and only those crosspoints not in this new path are released. It is not described how the new crosspoints are operated. It is suggested that the access wires may be used for class-of-service signalling but no details of such use are given.