PURPOSE: To incorporate a door phone call equipment permitting a door phone call by using a door phone adaptor in a system and to enable the door phone call between door by a telephone set and any door phone call device.
CONSTITUTION: The line wire, extension, and door phone calls can be performed by a telephone set by switchingly forming speech paths between the line wire and the extension, between the extensions, and between the extension and the call line. The telephone exchange is provided with output terminals T1 and T2 connecting the door phone call device performing the door phone call through a door phone adapter. When a call comes from the door phone, a calling signal is supplied from an output interface 21 to the door phone adapter. The output interface 21 detects the door phone call device responds to the calling signal. This output interface 21 forms the speech path between the door phone and the cordless telephone set through the door phone adapter at the time of the response of the cordless telephone set.
SUZUKI YOSHIHARU
KASASHIMA YASUSHI
