Abstract: Selective addresses and/or emergency messages are transmitted between individual stations by using a calling signal consisting of a synchronization signal and an address signal (SS and AS) sent out by a transmitter. The address signal (AS) used is a FSK signal which forms a diversity pair by being subdivided into two identical m-ary FSK signals. The type of operation used is a Channel in Band Scanning. The apparatus contains an address signal receiver which is realized by Real Time-Digital-Signal processing. As a result, the desired participating stations and only these can be reliably and unequivocally activated. In addition, the process is extremely insensitive to interferences.