My Glass Break Detector caused an apparent false alarm.  What could be wrong?

There are several types of Glass Break Detectors.  We have installed several thousand of these units over the years.  They are generally reliable when properly applied.  You also need to be aware of certain things that will "bother" them, however, most of those are things that occur while you are there to run interference with the consequences.  This guide will deal with only the most common types supported by Reliance Alarm Company.  It will serve as both a troubleshooting checklist and as a guide to help you recognize and avoid potential causes of false alarms.


Single and Dual Technology Glass Break Detectors

Sensitivity adjustment too high for environment

Dual Technology:  Most of the new designs have no adjustment "pot."  They either work or they don't.  These require two things in order to trip.  First, a low frequency shock wave has to occur, as when a rock hits a pane of glass and bends it inward.  Then a high frequency noise is needed, as the glass shatters (and falls).  Several manufacturers make these.  Hardly anybody installs the single-technology units any more.

End-User Testing:  These units should pass the "clap" test described below for single-technology units.  They may pass the jingling key test if you have the right key ring and the knack.  However, a dedicated testing box is needed to check these properly. 

Single Technology:  These earlier units were known as "AFD's," short for "Audio Force Detectors."  They were made by Unisec.  They have filters that are tuned to the high frequency of shattering glass but they will also respond to grossly loud sounds like that of a tempered glass panel breaking or a door jamb being broken in.   These can be recognized by a small hole on the face that has an adjustment "pot" inside.  A big caution is that the pot is accessible to tampering and also invites adjustment by unqualified persons.  Only a qualified technician should adjust these.  The hole is supposed to be covered by a small sticker, however many are bare.  The lowest setting is not really "off."  The lowest settings are meant only for very small, resonant rooms like tiled bathrooms.  The highest settings are meant for large, expansive areas with absorptive materials like plush carpeting, heavy draperies, etc.  We occasionally find one of these turned all the way up when we are called in response to false alarms.  We usually suspect it may be the result of a handyman testing with improper test apparatus.  The manufacturer sells a dedicated tester for these.  It's the most valid tester short of breaking a window.  Later units have a  set of "dip" switches inside for adjustment.  They have to be pulled out of the wall and opened up to get at the switches.  Again, only a qualified technician should adjust them.  

End-User Testing:  You can check for a grossly malfunctioning unit yourself, however:  First, if you clap your hands a foot or so in front of the unit and can trip the detector, it is either set too high or it has lost its "discrimination" capability.  Lightning or static damage is the most likely cause for that and a new unit is the solution.  Second, if you jingle your key ring immediately in front of the unit, it should trip.  (Give it a good shake.  You may have to borrow a couple different sets of keys to find a set the detector likes.)  If the unit fails to trip, call us for further advice and possible service.  Bear in mind that loosened or corroded connections are just as likely a cause of false activations as anything else.  Finding and correcting that is a matter for your technician to handle.

Animal noises.  We know a couple of dogs that reportedly could trip the old AFD's.  A detector update will probably solve that.

Commercial aluminum doors squeaking have been known to trip dlass break detectors when entering or exiting.  Oil is the obvious answer, but it's not permanent.  This can often be resolved more permanently by programming an entrance-exit delay on that particular detector zone instead of having an instant alarm.

Appliance and Machinery noise can trip glass break detectors under some conditions.  This is a matter for your technician to solve.