Simplex GSA4098-9792 TrueAlarm Standard Sensor BaseTrueAlarm sensor bases contain integral addressable electronics that constantly monitor the status of the detachable photoelectric or heat sensors. Each sensors output is digitized and transmitted to the system fire alarm control panel every four seconds. Since TrueAlarm sensors use the same base, different sensor types can be easily interchanged to meet specific location requirements. This feature also allows intentional sensor substitution during