GB608388A - Improvements in or relating to marker selection control systems such as are used in automatic telephone systems - Google Patents

Abstract

608,388. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Feb. 21, 1946, Nos. 5484 and 5485. Convention dates, Feb. 21, 1945. [Class 40 (iv)] In a marker selection control system of the type in which simultaneous hunting takes place by several selectors over the same marking multiple, and each marking device is provided with an individual current source; after a selection has been made, a further test is performed to check that the selection conforms with the position of the marker, and if the latter test fails, owing to a cross-connection having occurred, hunting is resumed. As shown in Fig. 2, a selector is driven by its electromagnet R in search of the group marked by MW, to the first contact of which group relay T operates in series with the individual current source S, followed by D which disconnects T and connects up the outlet testing relay Gt, under the control of which the selector hunts for a free outlet in the group selected. Operation of Gt brings up Sh and E, which reverses the current flow through T and reconnects it in the test circuit. If the selector is on the marked level, T re-operates and brings up the end of selection relay FS. If, however, the selector is not on the marked level, then owing to the slightly different times of operation of the sets of relays Gt, T and E of different selectors, T does not re-operate, but F comes up, disconnects wiper t and releases D to restart the search. Commoning of marking wires over the windings of the N relays is prevented by the rectifiers placed in series with the relays. In the modification of Fig. 3, the marker contacts and the group multiples in the bank of wiper t are connected to different potentials derived from the rectifiers U1, U2 ... and the check is made by a relay set A1, A2. On the operation of E after the selector has stopped, A1 comes up and connects A2 between the wipers t and MW, so that if the selection is correct and the wipers are both at the same potential, A2 remains unoperated and FS pulls up. If, however, the wipers are on different groups, A2 comes up, the subsequent operation of F releasing D to restart the search.