Distortion-free Compression of Telephone Signals in Multichannel Communication Lines

We consider the compression of digital telephone signals transmitted by multichannel communication lines. In principle, the capacity of such communication lines can be doubled by compression, using the existing hardware. The symbol error rate does not increase, so that universality of the communication channel is preserved (i.e., not only telephone signals, but any digital data can be transferred without corruption). The compression methods are based on known classes of universal codes.