相關(guān)元件pdf下載：4082 2n3904 4050 4072 
this is a complete alarm system with 5 independent zones suitable f a small office home environment. it uses just 3 cmos ic's features a timed entry / exit zone, 4 immediate zones a panic button. there are indicats f each zone a "system armed" indicat. the schematic is as follows:each zone uses a nmally closed contact. these can be micro switches stard alarm contacts (usually reed switches). zone 1 is a timed zone which must be used as the entry exit point of the building. zones 2 - 5 are immediate zones, which will trigger the alarm with no delay. some rf immunity is provided f long wiring runs by the input capacits, c1-c5. c7 r14 also fm a transient suppresser. the key switch acts as the set/unset reset switch. f good security this should be the metal type with a key. at switch on, c6 will ge via r11, this acts as the exit delay is set to around 30 seconds. this can be altered by varying either c6 r11. once the timing period has elapsed, led6 will light, meaning the system is armed. led6 may be mounted externally (at the bell box f example) provides visual indication that the system has set. once set any contact that opens will trigger the alarm, including zone 1. to prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. this will disge c6 start the entry timer. the re-entry switch could be a concealed reed switch, located anywhere in a do frame, but invisible to the eye. the panic switch, when pressed, will trigger the alarm when set. relay contacts rla1 provide the latch, rla2 operate the siren buzzer.
