| 摘要 |
PURPOSE:To improve the reception sensitivity of a master equipment, by forcibly switching a simultaneous transmission-reception system to a press-to-talk system by providing in aninterphone unit, consisting of a trnsmitter-receiver and duplex- systemsubordinate equipment, a switching unit which allows the speaker of the subordinate equipment ot operate as duplex one. CONSTITUTION:With selection switches SSn and SSn1 closed, transistor TR becomes ON to open contact Km via relay K. Sound from microphone MIC of subordinate equipment 2n is sent ot receiver R by way of amplifier A4 and hook switch S2. With change-over switch S5 opened, amplifier A3 operates. Signals from the subordinate equipment are therefore inputted to microphone-speaker SP and then outputted from receiver R through amplifier A3. Thus, reception can be attained while the reception sensitivity is improved. |
