Call system for time-division, delta-code switching network

Claim 1

A call transmission system for a time-division Delta -code switching system comprising subscriber''s telephone sets each including a Delta -coder unit for converting incoming Delta code pulses into speech signals, a clock pulse generator, means for synchronizing said clock pulse generator by said incoming Delta -code pulses, means for synchronizing said Delta -coder unit by said clock pulse generator, a keyboard arrangement for generating variable call pulse combinations coded in a binary code, fixed pulse combinations framing said variable call pulse combinations and a predetermined number of pulses of a given polarity forming a group for identifying a call pulse combination, the bits of the said call pulse combinations and framing pulse combinations and the bits of said identifying group having the same frequency as the Delta -code pulses, and a timedivision switching network including a clock pulse generator, subscribers'' equipments each comprising a pulse stretcher circuit for stretching the Delta -code pulses the pulses of the call pulse combinations and framing pulse combinations and the pulses of the identifying group received from the telephone set, a phase-shifter circuit for bringing the stretched pulses into phase concordance with the switching network clock pulse generator and a sampler for sampling the stretched and phaseshifted pulses in time slots respectively allotted to the subscribers, a call number register for receiving the call pulses combinations and the framing pulses combinations, call digit registers for receiving the call pulse combinations, a counter circuit for counting said pulses of a given polarity and a switching circuit controlled both by said counter circuit and call number register for directing the Delta -code pulses towards the outgoing subscriber''s lines of the switching network and the variable call pulse combinations towards said call digit register.