Call waiting and alternating method keyphone

The method provides a function to transfer communication to inner line subscriber who was stand-by not hang on current conversation and a function for certain inner line subscriber to transfer call from trunk to another inner line subscriber in busy. The circuit includes a tone generator (40) for generating tones, a stand-by music generator (50) for providing stand-by music to sender during stand-by or transfer, a complex frequency generator (60) for sending digit dialled by multi-button phone to trunk-side, and a switching circuit (70) for switching communication path.