Circuit Project Electronic

Battery Powered One Time Alarm Only with IC 4001
Sunday, November 9th, 2008

This is a single zone alarm - with independently adjustable Exit, Entry and Siren Cut-Off timers. It will accommodate the usual types of normally-closed input devices - such as magnetic-reed contacts, foil tape and PIRs.
When the alarm is activated - the Siren will sound for up to 20-minutes. Then it will switch off - and [...]

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One-Time-Only Burglar Alarm
Sunday, November 9th, 2008

This alarm is designed to sound its Siren only once. That is - when the alarm is activated - the Siren will sound for a preset length of time. Then it will switch off and remain off. The alarm will not re-activate.
The basic circuit has a single zone with independently adjustable Exit and Entry delays. [...]

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Automatic Intruder Alarm with IC 4011
Friday, November 7th, 2008

It’s easy to use. First check that the building is secure and that the green LED is lit. Then move SW1 to the “set” position. The red LED will light. You now have about 30 seconds to leave the building. When you return and open the door - the Buzzer will sound. You then have [...]

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