| 摘要 |
PURPOSE:To prevent interference and to improve selectivity by using signal modulated by a calling signal of a specific frequency band as a signal from a transmitter and using a crystal oscillator of turning fork type for a receiver. CONSTITUTION:A transmitter 10 modulates a fixed transmitter 11 and a variable transmitter 13 by a modulator 14 and outputs them as a transmitting signal. The variable transmitter 13 oscillates the signal of the frequency selected by the operation of an operation part 12 at the frequency band of 25-80kHz. A super-regenerative receiver 20 amplifiers the received signal, after that, detects whether it is the frequency inherent in the super-generative receiver 20 or not by a tuning fork type crystal oscillator 21, when it is the frequency inherent in the super-generative receiver 20, it rings the bell 26 through a bell oscillating circuit 25 and oscillates a receiving signal through an oscillating part 27 and a return antenna 28. Thus, the interference can be prevented and the selectivity for the frequency can be improved. |
