Circuitry for connecting the first call signs and advanced call signs in telephone installations in particular pabcanlaeg by means of a predetermined vekselstroemstakt

摘要

1482366 Automatic exchange systems SIEMENS AG 10 Dec 1974 [14 Dec 1973] 53278/74 Heading H4K The supply of ringing current is controlled by a gating arrangement including a counter which determines the periodicity of the bursts of ring- ing current. The circuit arrangement, Fig. 1, can be produced in monolithic integrated form and one such circuit may be provided for each line circuit of the exchange. In operation a ring command signal is supplied on wire 1 to enable a 0-15 binary counter to count a 3À125 Hz clock pulse train supplied on wire T and derived from the mains voltage. Whilst the counter counts from 0-2 gate G6 is enabled to connect a ringing signal to the subscriber's line. For the counting range 3-15 gate G6 is inhibited to provide a pause. The counter is reset from its final state via gate G1 and the sequence then repeats, such that approximately one second bursts of ringing signal separated by approximately 4 second periods of silence are produced. The removal of the command signal trips the ringing.