System Sensor makes these relays for 4-wire smoke detectors. They are used for power supply supervision.
Specifications
Operating Voltage: 9 to 40 VDC ( 9 to 35 Vrms for unfiltered full wave rectified supplies )
Operating Current: 20 mA max.
Operating Temperature Range: –22ºF to 140ºF (–30ºC to 60ºC)
Storage Temperature Range: –40ºF to 185ºF (–40ºC to 85ºC)
Humidity: 10 to 93% RH non-condensing
Wire Length: 8″ min. (203 mm)
Dimensions: 0.91″H x 1.65″W x 1.22″D
(23 mm H x 42 mm W x 31 mm D)
Accessories: Four wire nuts
One piece of double sided tape
One 11/4″ screw
Contact Ratings: 120 VAC 0.5 A max. (resistive load)
30 VDC 3A max. (resistive load)