| 摘要 |
PURPOSE:To increase the operability of a selected interphone, by selecting the interphone for communication and switching the state of reception and the state of transmission of the interphone selected by a press-to-talk switch. CONSTITUTION:Plural sets of terminal devices and interphones are connected to a main controller via a common transmission line 1. In case the talking is carried out between an interphone C1 and another interphone, a channel selection switch 6 corresponding to the interphone to be called out is first operated. At the same time, a press-to-talk switch 12 is pushed for the speech transmission. This mode is sent to the main controller via a terminal logic processing circuit. The main controller feeds the control signal to the selected interphone to give the conduction and the reception mode to a switch 19. When the switch 12 of the interphone C1 is released, the main controller feeds the control signal in the same way to give the transmission mode to the selected interphone. |
