Duplex digital span conversion circuit arrangement

Claim 1

In a telecommunications switching system, a conversion circuit arrangement connected between a plurality of digital spans and a switching network of said switching system for converting received data from said digital spans, said conversion circuit arrangement comprising: said conversion circuit arrangement including first and second conversion circuit copies, said first and second copies operated to convert digital span data to data compatible with said switching network; each digital span of said plurality being connected to a first and second copy of one particular conversion circuit; CPU means connected to each of said first and second copies of said conversion circuit, said CPU means operated to selectively enable said first copy of said conversion circuit to receive data from said connected digital span or said CPU means alternatively operated to selectively enable said second copy of said conversion circuit to receive data from said connected digital span; said CPU means operated to initially select said first or said second copy of said conversion circuit for receiving data as an active copy and said CPU means further operated to instantaneously select a standby copy of said conversion circuit for detection of a fault of said active copy of said conversion circuit preventing switching network service interruption; transformer means including first and second copies, said first and second copies of said transformer means connected in parallel to a particular digital span; said first copy of said transformer means being connected to said first copy of said conversion circuit; said second copy of said transformer means being connected to said second copy of said conversion circuit; said first and second copies of said conversion circuit respectively connected to first and second copies of said switching network; impedance control means connected to said CPU means and operated in response to a first signal of said CPU means to select a first impedance value of said conversion circuit copy for a first value of said first signal or alternatively to select a second impedance value of said circuit for a second value of said first signal; voltage detection means connected to a corresponding copy of said transformer means and to said impedance control means, said voltage detection means being operated in response to said digital span data to produce a second signal representing a peak amplitude of said digital span data; voltage divider means connected to said voltage detection means and operated in response to said second signal to produce a third signal representing approximately one-half the amplitude of said second signal; and comparator means connected to said corresponding copy of said transformer means and to said voltage divider means, said comparator means being operated in response to said digital span data and to said third signal to produce an output signal for said digital span data having an amplitude in excess of said amplitude of said third signal, said output signal being said data compatible with said switching network.