I can arm then disarm the above and the Led's flash about every 12 sec. They don't flash when the system is armed.

To me this is similar to an alarm system that has been activated (Armed) and a PIR has picked up movement, the siren/light goes on for 20 minutes then goes off, and then the LED flash to let you know that movement was detected.

Appreciate knowing out to stop the led flash as I want to install the siren inside our house to annoy any intruders.

Thanks

Peter