Time division multiplex telecommunication exchange

Claim 1

Time division multiplex telecommunication exchange, of the type comprising a number of line circuits to which incoming and outgoing transmission channels are connected, which transmission channels are arranged for the transmission of bit streams divided into bit groups, switching means connected to each transmission channel for the transmission in time division multiplex of bit groups from selected line circuits of the incoming transmission channels to selected line circuits of the outgoing transmission channels, a common bus line on which said bit groups are conducted through said switching means, the improvement wherein each of the line circuits for the incoming transmission channels comprises a separate comparator means for comparing each bit group received with the preceding bit group and gate means responsive to said comparator means for preventing a bit group from being supplied to the switching means when the comparator detects equality, said switching means selecting and allocating a free time division multiplex time slot only in response to the passage of a bit group through said gate means and wherein the line circuits for the outgoing transmission channels comprise means for the retransmission of a bit group when no new bit group has been received from the switching means within a predetermined time.