SD2: Photoelectric smoke alarm for Watchdog environmental monitoring systems 

SD2 smoke alarm is a photoelectric type unit for use as an alert and relocate device in residential and commercial applications.

SD2 is a low voltage smoke detector with built in interface to allow monitoring through the ports of an environmental or power+environmental monitoring unit equipped with analog-sensor inputs. A 12VDC power supply is attached and a and a 25 feet length, 2-conductor alarm wire is included for easy installation.

When in alarm state, the monitored reading will drop below 10.

Each smoke alarm has a solid state piezo signal to warn and alert to the presence of threatening smoke.

SD2 photoelectric smoke alarm is designed to detect the smoke that results from an actual fire. Consequently, it is uncommon cigarette smoke or normal cooking smoke to cause an alarm.

SD2 is a 120VAC photoelectric smoke alarm/detector with 9VDC battery back-up as an auxiliary power source in the event of an electrical failure. It features a warning signal for low or missing battery.

SD2 smoke alarm operates on the photoelectric light scatter principle. The unit's sensing chamber houses a light source and a light sensor. The darkened sensing chamber is exposed to the atmosphere and designed to permit optimum smoke entry from any direction while rejecting light from outside the smoke alarm.

The light source is an infrared (invisible) LED which pulses every 8 seconds. The light sensor is a photodiode matched to the light frequency of the LED light source.

Under normal conditions, the light generated by the pulsing infrared LED is not seen by the light sensor, as it is positioned out of the direct path of the light beam. When smoke enters the sensing chamber, light from the pulsing LED light source is reflected by the smoke particles onto the photodiode light sensor.

At the first sighting of smoke, the device is put into a pre-alarm mode. This is indicated by a rapidly flashing LED on the face of the smoke alarm. Once the light sensor confirms smoke for 2 consecutive pulses inside the chamber, the light sensor produces the signal necessary to trigger the alarm and sound the electronic horn.

This technique of verifying the smoke condition, combined with a 5-to-1 signal-to-noise ratio, substantially reduces the possibility of nuisance alarms.

Features and Benefits
• 120VAC and 220VAC with 9VDC battery back-up
• Low or missing battery indicator
• 9VDC alkaline battery included
• Patented three-position test switch
• Includes 90db piezo solid state non-latching horn
• Tandem connection up to 12 units; 6 on relay models
• Nominal 3.0% sensitivity
• 5:1 signal-to-noise ratio
• Pulsing LED sensing chamber
• Full insect screen
• Solid-state LED condition indicator
• Quick-disconnect wiring harness
• Mounting hardware adapts to standard junction boxes
• Protective high air velocity gasket
• On-site maintenance washing program
• Compliant with NFPA Standards
• Temporal 3 evacuation sounding device (9123 and 9223)