Can anyone throw some light on this:

I have a site with a T530 panel (Non Addressable). Each of the 4 zones has one optical and one ionisation detector. One of the detectors LED flashes at a predetermined rate, whilst the other LED stays off. I didn't note whether its the optical thats flashing or the other one. Both detectors tested ok , and the LED burns solidly when smoke is applied, so all appears to be working ok. I think this occurs on other sites, just wondering if there is a reasonable explanation.

is it the eol device that flash's i know with the rafiki twinflex kit the detectors flash but also the old thorn heads used to flash and so did the old zettler ones flashed green when healthy

The panel you have is a Thorn panel so I'm guessing the detectors will be Thorn too. The opticals give a flash of their LED every so often but the ions don't. When testing the opticals you'll notice the LED start to pulse faster just before the detector goes into alarm.

The panel you have is a Thorn panel so I'm guessing the detectors will be Thorn too. The opticals give a flash of their LED every so often but the ions don't. When testing the opticals you'll notice the LED start to pulse faster just before the detector goes into alarm.

Yes, thats exactly what happens.....so I guess its normal and nothing to concern myself about...Thanks for your reply