Circuit arrangement for the equalization of digital signals received in analog form

DETAILED DESCRIPTION A digital subscriber line system illustrated in FIG.
1 could be designed, for example, for the duplex transmission of digital signals over a two-wire line in the duplex channel system.
A subscriber line system of this type first converts, with the aid of a coder COD the binary signals SD, such as telecommunications signals, that are to be transmitted over the two-wire line--into multistage signals for example, into digital signals coded according to the 2B1Q line code.
The 2B1Q line code, which is a quaternary code with the levels of +1, -1, +3 and -3, is well known to those skilled in the art.
The digital signals are then pulse--shaped and converted to analog signals by a pulse shaper IF.
The analog signals are received by a hybrid arrangement GA.
Analog signals received by the hybrid arrangement GA are outputted to at the digital signal receiver EE.
The input of this receiver includes an analog/digital converter A/D, which obtains samples from the received analog signals, for example, at an interval corresponding to one bit length of the transmitted digital signals and converts each sample into a digital signal having a prescribed number of bits.
The synchronized clocking pulses required for this purpose are understood to be supplied by a clock unit not shown here.
The digital signals supplied by the analog/digital converter A/D first pass through a compromise equalizer KE and are then fed successively to a subtractor SUB1 which simultaneously receives compensation signals from an echo compensator EK.
These compensation signals compensate for the echo signal components contained in the digital signals, which, during the transmission of a digital signals in analog form over the two-wire line as described above, have been superimposed on the received analog signals as the result of reflections on the line or as a result of incomplete decoupling of the transmission paths of the hybrid arrangement.
Echo compensation is well known to the prior art.
The digital signals, now compensated, are then routed, for any further processing that may be necessary, through a control amplifier (not shown here) to an equalizer arrangement, which eliminates most of the distortions of the digital signals caused by the electrical characteristics of the two-wire line which have not yet been eliminated by the compromise equalizer KE