Synchronization circuit for visual/audio alarms

Abstract

A strobe alarm system which includes multiple normally self-timed strobe circuits connected in a common loop to a fire alarm control panel, and a sync control circuit, which may be incorporated in the fire alarm control panel, for causing the strobes to flash in synchronism at a predetermined rate which will insure that a person viewing the multiple strobes would not see flash rates higher than the predetermined synchronized rate, which is preferably less than five flashes per second. The sync control circuit does not interfere with the supervision functions of the alarm system, and when an alarm condition is present it supplies power to the strobe circuits which it then interrupts once every flash cycle to cause a sync trigger circuit in each strobe to fire its flashtube, and to reset the internal timer of each strobe to ready it for arrival of the next sync signal. Each strobe circuit in the loop includes a resettable timer for recycling its own flash unit in a non-synchronous fail-safe mode in case the sync signal should fail to appear within a finite period following the last previous flash. That is, normally the strobes are all fired at the same time in response to sync signals applied to their sync trigger circuits, but in the event the sync signal is lacking the strobes will continue to flash, each at a rate determined by its internal timer.