DE1487839

1,111,498. Automatic exchange systems. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 2 May, 1966 [5 May, 1965], No. 19203/66. Heading H4K. In a system employing cross-point switches, e.g. of the reed relay type, in tandem, pathseeking in response to the marking of input and output terminals is effected over the C-wires which include negative resistance devices consisting of cross-coupled transistors 5, 6 together with a transistor 4. When an idle path is seized, the resistance of the C-wire is much reduced, the controlling relays such as KA, KB, KC energize and hold over the transistors 4 which are now saturated, and the seizure of any other path is prevented.