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Thanks for trying to lend a hand; the more people the better! The flashing LED *will be replaced (by me)* with an optocoupler, which is an 8 pin part that looks like an LED to the device (input 2 pins), but provides an open collector phototransistor output (short to ground opposite 2 pins) on the alarm device providing optical isolation between the two. The LED is fully encapsulated and won't be visible once I change this one part - if a dry contact closure is needed, I can drive a relay with the optocoupler phototransistor and it will click on/off once per second, though the wear&tear on the relay is undesirable, so I'd much prefer to keep it all silicon devices. The people who designed the safety device put the blinking heartbeat LED in so that *IF* it's blinking, it's working. It's an output line from the microprocessor inside meant to be human readable, but due to this application, it needs to be monitored and supervised, so my optocoupler circuit has a built in periodic self-test and will signal a trouble line if anything else goes wrong. That part is easy to do in hardware with a soldering iron. Now the problem I have is a contact closure who's "normal" state is opening/closing 1x/sec and "alarm" state is stuck open or stuck closed. There could be a hardware failure, or even a software failure causing it to freeze up. Both of those 2 conditions mean something died, and it needs attention. That's the part I'm having trouble figuring out how to program a panel to connect to. My more hardware centric idea was to take a capacitor, use a large value (1M-ohm) resistor to keep it charged slowly and use the periodic signal to short it to ground, along with another capacitor that is charged (tied to 5v) by the periodic signal with a "bleeder" resistor to 0V. Alarm condition would be either of these 2 capacitors reaching their level set by the always on resistor (high or low) because it can get "stuck" with the LED on or off, so I have to handle both cases. Lastly, as this is a safety device, it has its own ALARM output dry contact, but the designer did not put in any sort of "trouble" output, just the blinking LED - without that a human must make rounds looking for blinking lights. thanks for your help! I really appreciate it. Fred

Hello from California! I'm a microwave/RF engineer by trade, I've installed Ademco systems for myself and for friends, as well as the 900MHz (USA) Alarmnet digital polled radio backup to dialup or multiplexed leased lines. Alarms are NOT part of my job, but from what I learned programming the Ademco equipment, I never saw a configuration for a heartbeat pulse signal monitor from other 3rd party equipment. I have a dilemma on how to accomplish this - my customer has 3 electrical devices that by law here must be monitored for failure of the safety device itself. The device does this by providing a roughly 1 blink per second green LED to communicate its status. If the device were to "seize up", it would put human life at risk, thus the need to make sure it's functioning, and the green light is blinking just like it always is. I can replace the LED with an optocoupler and get the emitter&collector of a phototransistor output. It can be made to resemble a contact closure to a panel zone, but it's normal (i.e. no alarm) state is opening/closing about 1x per second (this can be stretched longer in cases of maintenance, like a firmware update that may take 30 seconds - I'd set the alarm condition to be zero blinks in 60 seconds) The problem is most low-end alarm panels see this open/shut/open/shut behavior (heartbeat led) as a "swinger" or a door that isn't shut right and keeps re-triggering that zone in the wind. Does anyone know of a panel with a zone configuration specific to a pulsed on/off signal representing a "closed" state (like a door) and the lack of a signal, or a stuck on/stuck off representing the Alarm condition? If not a panel, has anyone seen a pre-conditioner that would take the heartbeat blink and convert it to steady closed / steady open on alarm? I'm trying to find a commercial off the shelf solution rather than a custom design just to monitor a blinking LED / transistor logic output on 3 systems. Thanks for your thoughts here! Fred