I just ate dinner at a local restaurant with my family and while in the coat room I noticed the maintenance closet was open. So i decided to take a peek inside. There was a fire alarm communicator that seemed to be connected to the security system. The thing that was weird was that the buzzer inside was at a “half buzz”. The trouble light wasn’t on but the buzzer (kinda) was.
Any explanation behind this or has anyone seen/heard of this happening before?
I have seen some panels that have a brownout circuit or power supply monitor circuit powered by their own small power supply circuit. Sometimes the small filter capacitor in these circuits dry out over the years thus loosing capacitance. The reduced filtering causes more ripple on the power for the power transfer or trouble relays. This can cause the relay to buzz. Sometimes the relay buzzing can be quite loud.
Any idea on the make/model? Buzzing could have also just been the transformer inside, sometimes if they hit the case just right they can rattle a little.
But the buzzing was coming from the piezo, because i covered it up with my finger and the sound stopped.
Ah ha, withholding important evidence!
It could still be a power supply filtering issue. Ripple in the power supply could cause the circuit that drives the piezo to oscillate slightly at the ripple rate. Usually 120 Hz.
I wonder too if maybe the “trouble silence” switch was activated with no trouble condition present. The FC-72 panel in particular comes to mind. If you leave the trouble silence switch in with no trouble you will get the sonalert beeping slightly with a dim general trouble light.
Also, the Silent Knight 5104 dialer will beep if an alarm condition is present and won’t show any LEDs lit until you press the silence switch on the side. But the only three LEDs are power, trouble, and silenced. Looks like this:
