The photo sensor (P/N 63-1052/63-1058) provides peer-to-peer digital protocol for reliable, fast communications. The sensor includes a tri-color LED for instant indication of device status. An acclimate feature is defaulted ON to provide optimum fire detection response. This feature allows sensors to respond to a particular environment and its operating parameters are maintained within non-volatile RAM in the sensor. Dual Alarms (night and day sensitivity) with threshold settings between 1.3 - 3.6%ft. Dual Pre-Alarms with threshold setting between 0.5 - 4.0% ft.