Need one modification to a burglar alarm system

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I used to do custom circuits back in the 70s but have got out of the habit until just now. I bought a kit from Cheney Electronics to build a professional burglar alarm. I have it working. It will give a 30 second delay to allow you to leave a protected area, it will give you a 30 second delay to turn it off when you come back into a protected area, and it will sound an alarm for one minute then turn off.

The problem is if the open circuit (which triggers the alarm) is not closed after the alarm sounds, it will not reset and will sound again for a minute.

I don't want this. I want the alarm to sound only one time for a minute or so and then turn off. It would no sound again until he alarm had been turned off and would then be enabled for the next event.

So, I think what I want is for a device to do the following:

1. be powered on
2. accept only one 9 volt signal to an input
3 Trigger a relay that will stay active for a set variable time (1-5 minutes)
4. Ignore any further transitions of the 9 volt input.

I'm betting there is such a device out there, but I can't find it clearly explained as to how it works.

It also need to be low power as it waits for the 9 volt input and it's power supply should also be 9 volts.

Any ideas??

[KMoffett]

Assuming this is what you are using [url]http://www.electronickitsbychaneyelectronics.com/prodinfo.asp?number=C6785[/url], do you have a schematic?

Ken