| 摘要 |
PURPOSE:To enable a master station and subordinate station to know the engagement of the other stations mutually by indicating the engagement of the master station at the subordinate station through switch operation while indicating the engagement of the subordinate station at the master station all the time, by using a tone signal which indicates the engagement with a line wire. CONSTITUTION:The master station is provided with a transmitter receiver and connected to the subordinate station by radio, and the interphone of the subordinate station can be connected to the line wire of the subordinate station. With the handset of telephone set 2 off the hook, circuit connection detecting circuit 19 of the master station operates and while relay RY-3 cuts off the circuit to the subordinate station, circuit in-use signal generating circuit 20 is driven to generate tone signal f3. On receiving tone signal f3, the subordinate station changes over the flip-flop of the answer switch to generate a circuit in-use signal from the speaker of the subordinate station. When the subordinate station is engaged, the answer switch is closed to generate tone signal f2, which is received by the master station to continue to excite relay RY-1, and then relay RY-2 is excited to display the state on light emitting display element 23. |
