Key telephone system having a plurality of telephone numbers to key telephone set

摘要

This invention enables the key telephone system to send a busy tone to a party calling on a main extension number when a telephone call to the main extension number is received when a pseudo extension number is in use.The receiving mode is memorized in the memory of the main unit. When a telephone call to the main extension number is received when the pseudo extension number is in use, a busy tone can be sent to the calling party on the main extension number.According to this invention, the calling party thus knows that the key telephone set, which is the destination of his call, is busy.