| 摘要 |
PURPOSE:To make it possible to change an in-use transmitter of hot stand-by constitution, sending out a bipolar signal, over to a stand-by transmitter or vice versa at a high speed. CONSTITUTION:While signals A and A' are applied to bases of transistors 14 and 16, signals B and B' are applied to bases of transistors 15 and 17 and while control signal C applied to the base of transistor 18 is held at a high level, control signal C' applied to the base of transistor 19 is held at a low level. As a result, output OUT1 of the secondary side of an output transistor is a bipolar signal, but since stand-by transmitter 12 has transistor 19 cut off, transistors 16 and 17 are also cut off by signals A' and B', and consequently impedance viewed from the secondary side of output transistor 21 is infinite, exerting no influence on the amplitude of OUT1. Control signals C and C' are held in level reversely, so that the in-use side will be changed over to the stand-by side. |
