| 摘要 |
PURPOSE:To suppress noise from a room by providing a switch circuit which selects a high pass filter circuit when a terminal equipment does not output a DC current and selects a 2-way pass circuit when the terminal equipment outputs a DC current. CONSTITUTION:A protector 1 is connected to a terminal equipment 2 via an indoor cable 16 and a signal is fed to a communication control section 15 via a capacitor 12. A transistor(TR) 14 is a DC switch element and a DC current is supplied to the protector 1 when the TR 14 is conductive. When the control section 15 sends an incoming signal, the TR 14 is turned on to drive a relay 10 in the protector 1 and a contact 8 of the relay 10 is thrown to the position of a strap line 9, then an incoming channel is secured. When the incoming signal is stopped, the TR 14 is turned off to stop the DC current and to reset the relay 10, then the contact 8 is thrown to the position of a high pass filter 11 and only an outgoing channel is formed. Thus, the noise from the inside of the room is suppressed with a simple circuit without giving hindrance onto communication. |
