| 摘要 |
<p>PURPOSE:To interface between plural portable telephone sets and one power amplifier by providing a means varying a substantial gain of power amplifier and a control section controlling variably the gain of the gain variable means. CONSTITUTION:When, e.g. one portable telephone set A is connected to a power amplifier 1 via a high frequency signal line 20 and a control signal line 21, a control signal representing the connection of the telephone set A is inputted to a control section 4 via the line 21. The control section 4 operates simultaneously changeover switches 12, 15 of a transmission section 2 and a reception section 3. Since the attenuation of an attenuator 10 is adjusted so that a transmission signal from the telephone set A is in matching with an input interface level of an amplifier 8, the transmission with an optimum level is attained. Since the reception signal is attenuated at the reception section 3 by an attenuator 16 so as to be in matching with an input interface level of the telephone set A, optimum reception is implemented. On the other hand, when a portable telephone set B is connected, the switches 12, 15 are changed over and the transmission and reception at an optimum interface level is implemented by attenuators 11, 17.</p> |
