A communication system comprising: at least one first communication device configured to communicate in half duplex mode using a first encoding-decoding format; at least one second communication device configured to communicate in half duplex mode using a second encoding-decoding format; a third communication device configured to communicate in half duplex mode using the first format; a fourth communication device configured to communicate in half duplex mode using the second format; wherein the third and fourth communication devices are configured to communicate with each other in half duplex mode using a third encoding decoding format.