With the countdown timer, I have inconsistent trigger issues.  Sometimes it works perfect but other times it does not trigger on the input signal.  The input comes from my liftmaster universal receiver (model 850LM).  Its a 12v pulse when I press a remote control button.  I originally connected the output of the 850LM directly to the input of the timer high trigger but it caused feedback issues so I installed a mini 12vdc relay and used that to trigger the timer.  I can connect directly to my gate opener, bypassing the 850LM but it also caused feedback issues when I connected the output of the alarm positive to the timer.  Even though it will drive an alarm beeper, it caused strange feedback.  Any ideas on how to increase its reliability with trigger?  Do I need an opto-isolater?  If I just connect 12v switch to your timer it works fine, but thats not real world practical.  Thanks