| 摘要 |
PURPOSE:To detect communication request of other station even at transmission setup by allowing a signal to be forcibly transmitted intermittently for each short time at the transmission setup and detecting the presence of a reception signal during the pause period. CONSTITUTION:An antenna 1 is connected to a mixer 4 or a transmission signal amplifier circuit 12 by a changeover switch 2. An output of a local oscillation circuit 3 is fed to the mixer 4. An output of the mixer 4 is applied to an intermediate frequency amplifier circuit 6 through a filter 5 and further fed to a demodulation circuit 7. An output of the demodulation circuit 7 is applied to a tone detection circuit 9 and a sound band pass filter 8, and its sound output is fed to a terminal 21 via a switch 17. An output of the tone detection circuit 9 is fed to a display circuit 11 via a time constant circuit 10. An output of a transmission stop signal generating circuit 15 and a transmission press signal are fed to the switch 2 and a transmission control circuit 13 via an AND circuit 14. The output of the transmission control circuit 13 and a modulation circuit 16 is fed to the transmission signal amplifier circuit 12. |
