| 摘要 |
PURPOSE:To prevent the occurrence of howling even in case of simultaneous reception loudening by stopping the function of a transmitter and setting the forced muting state where a dialing signal is given to a transmission input when the on-hook dialing state is set. CONSTITUTION:In the on-hook dialing state, interlocking switches SW1-SW3 are operated to close a DC loop passing a speaking circuit 2 and a loudening amplifier 6 is set to the operating state. Since a transistor TR Q1 is turned on and a TR Q2 is turned off by the switch SW2, the function of a transmitter T is stopped and preparations for transmission of the dialing signal to the transmitter T are made. Since a muting signal is transmitted simultaneously with transmission of the dialing signal by the operation of a dial key 4, a TR Q5 is turned on, and the input level of the amplifier 6 is reduced to make the sound volume proper.
|
