Abstract: A hybrid communication system includes a telephone unit and a host communication apparatus, such as a facsimile machine, either of which is selectively connected to a common external transmission line which in turn is connected to a telephone network. When a request for conversation has been received while the host apparatus was in communication operation, a call signal is supplied to the telephone unit automatically upon completion of the current communication operation to produce a ringing sound. When an operator picked up the handset of the telephone unit in order to use it for conversation but could not use it because the host apparatus was in communication operation, upon completion of the current communication operation by the host apparatus, a call signal is automatically supplied to the telephone unit to produce a ringing sound to apprise the operator of the fact that the telephone unit is now available.