Abstract: According to telecommunication standards relating to communication networks supporting an Asynchronous Transfer Mode (ATM), timing information relating to a Constant Bit Rate (CBR) service needs to be communicated between a source network entity and a destination network entity. Typically, the timing information is obtained by measuring a phase of an incoming CBR stream of bits at the source network entity against a synchronous standard, such as a master clock signal. However, where the stream of bits comprises multiplexed services, it is difficult to measure the phase of the parts of the stream of bits relating to a service of interest without first demapping or demultiplexing the stream of bits. Consequently, the present invention overcomes this difficulty by counting justification event amongst the stream of bits, the count of justification events corresponding to timing information relating to the service of interest.

Abstract: An arrangement for the demodulation of auxiliary low frequency channels in digital transmission systems comprising means (12) for receiving the transmitted signals, linear amplification means (13) with automatic gain control (AGC) (14) for the received signals, non linear discrimination means (15) for discriminating between logic levels in the amplified digital signals at the main channel bit rate, and subtraction means (16) for subtracting the output of the discrimination means from the amplified signals to obtain the auxiliary low frequency channel signals.