Method for achieving 180°phase invariant transmission in a PCM modem system

For communicating information from a transmitter to a receiver according to the PCM modem system using the equivalence classes (equivalence class), there is provided a method for solving the problem of the 180 ° phase shift in the communication channel to cause the transmission gabeul (garbled transmission). This is accomplished by mapping, the equivalence class identified by the material of equivalence classes in a way that it can be differentially encoded and decoded as not to be lost during the phase inversion of the channels. 2, the incoming bit stream 10 is applied to the modulus converter 12, the converter 12 to the mapping block 14 for mapping the structure of the type shown in Figure 1 the output of the modulus of the converter It is connected, with each equivalence class is provided with a label comprising a sign bit and a magnitude bit. Equivalence class, PCM modem systems, differential encoding, and decoding differential phase inversion