The Fenwal Models PSD-7157 and PSD-7157D Photoelectric Smoke Detectors respond to a broad spectrum of both flaming and smoldering fire conditions. The Detectors have advanced solid-state, low-voltage, surface-mount circuitry and are designed for 2-Wire and 4-Wire installation using the appropriate Detector base. The characteristic 360-degree detector design permits smoke entry from any direction. A unique sensing chamber design permits the operation of the Models PSD-7157 and PSD- 7157D in open areas with air velocities from 0 to 300 fpm and 0 to 4000 fpm respectively. The Model PSD-7157D is also suitable for duct housing applications in air velocities from 500 to 4000 fpm. The Detectors are designed for open area/duct housing applications per UL268/UL268A and may be installed in systems intended for Releasing Device Service through use of compatible Fire Alarm Control Panels. Two Red Light Emitting Diodes are located diametrically opposite each other so as to allow 360-degree viewing. Both LEDs continuously indicate the operating condition of the Detector. During standby, the LEDs flash once every six seconds. During alarm, both LEDs light steady at full brilliance. A double flash every six seconds indicates a detector with a sensitivity threshold threshold
outside acceptable limits. A unique gated output circuit design provides improved stability and transient suppression. Special signal processing techniques verify the presence of smoke before the detector will alarm. A fine mesh insect screen protects the chamber area and is used to avoid potential nuisance alarms. The detector head is installed into the base with a simple twistlock action. A locking feature is provided for vandal resistant security