Abstract: A security system (10), operable to produce an ALARM signal indicative of glass breakage in a region (16) in which a human being (24) may legitimately be present, has a human presence detector (12), a glass breakage detector (14), and an alarm signal activator (30) that includes a one-shot timer (52). A HUMAN PRESENCE DETECT signal (36, 38) output from the human presence detector triggers or retriggers the timer to produce an active output for a predetermined holdoff time interval T.sub.H. The active output causes a gate (58) to prevent a glass breakage alarm or GB DETECT pulse (46) from the glass breakage detector from reaching a control panel (34) and thus from triggering the ALARM signal if the GB DETECT signal occurs within the holdoff time interval after a HUMAN PRESENCE DETECT signal. Another gate (64) prevents a GB DETECT pulse (48) from reaching the control panel if that pulse occurs while the human presence detector is detecting human presence in the region (38).