Abstract: The present invention relates to a private branch exchange, a telecommunication system comprising such an exchange and methods of transmitting signals in subrate channels of a fullrate channel. The exchange comprises a switch control means, which allocates subrate traffic channels of the fullrate channel to voice and data, and a channel handling device (44), which comprises at least one voice channel means (66, 68, 70) connected to a respective channel input (22, 24, 26) and being arranged to compress signals appearing on this input (22, 24) or to pass at least part of each signal through unaffected. The compressed or passed signals are fed to a multiplexer (76), which multiplexes signals incoming from the voice channel means to outgoing signals for sending in a fullrate channel on a first telecommunication line (14). A demultiplexer (78) is also included for demultiplexing signals in a fullrate channel.