| 摘要 |
PURPOSE:To sense the stop of operation of a transmission circuit in advance and to continue the operation of the transmission circuit successively, by stopping the operation of the transmission circuit with the end of the set time after the application of an operation switch. CONSTITUTION:In closing the operating switch 14, a transistor (TR)17 is turned on until a terminal voltage of a capacitor 16 reaches a set level, and power is fed to the transmission circuit 18. A bias with a breeder resistor 30B is given to a TR30 forcedly during the charging of the capacitor 16. When the terminal voltage of the capacitor 16 reaches V2(V2<V1), the TR30 turns on, a signal from a tone generating circuit 35 is given to a speaker 13 to provide a notice of the transmission stop. In closing a switch 23, the operation of the transmission circuit is continued. |
