|This simple alarm uses a single Cmos 4060 - and features Exit, Entry and Siren Cut-Off timers.
Detailed Circuit Description
The Cmos 4060 Alarm is a single zone circuit - with automatic exit, entry and siren cut-off timers. It was designed for normally-closed input devices - such as magnetic-reed contacts - foil tape - PIRs etc. But it's easy to add a normally-open trigger.
Add A Normally-Open Trigger
After the exit delay has expired - pin 7 is high. If the normally-open contacts are closed - pin 7 will supply gate current to Ty1 - through Rx. This will trigger the SCR - and the activation sequence will proceed as before.