[Application of pyroelectric infrared sensor to radio control alarm system]

A radio control alarm system was developed, which is composed of a pyroelectric infrared detecting module, a radio receiving/transmitting module, a digital encoding/decoding IC, and a voice recoding/playing module. When somebody enters the surveillance area, the infrared sensor will receive and transform the radiant energy into electric signal, which is amplified by internal circuits, and then generates a control signal to start transmitting system. As the encoded pulse is modulated by the transmitting module, a radio control signal will be spread to space; When received, the signal will be demodulated, amplified, shaped and decoded to trigger the recoding/playing circuits, which play the recoded voice to awake watch people. The system mainly adopts the RDP-18 pyroelectric infrared detecting module, which has full function from signal receiving to output control. The whole device is a module configuration. It has the advantage of frequency stable, work reliable, no debugging, and a remote control distance of 1 000 m, and is suitable for use in many kinds of demands.