Method and apparatus for carrying out loopback test

Apparatus, for carrying out a loopback test in a data communication system having a first data communication station connected by a transmission path to a second data communication station, each of said first and second data communication stations having a transmitter and a receiver, comprising:

• a central processing unit, having an error checking means, for providing a loopback test signal and a test control signal;
• generator and control means, operatively connected to the transmitter and the receiver of the first data communication station and to said central processing unit, for generating first and second pseudo-random noise signals in dependence upon said test control signal and for controlling the transmission of said loopback test signal, wherein the first and second pseudo-random noise signals are transmitted by the transmitter of the first data communication station to the receiver of the second data communication station by way of the transmission path;
• detector means, operatively connected between the receiver and the transmitter of the second data communication station, for detecting the first and second pseudo-random noise signals and for providing the transmitter of the second data communication station with a return loopback test signal for transmission to the receiver of the first data communication station, wherein said error checking means is operatively connected to said generator and control means, and wherein said error checking means compares said loopback test signal with said return loopback test signal, whereby a malfunction of the second data communication station is detected.