The basic alarm system consists of an electronics unit and two breeching components. A light source directs a beam through the measured particulate, and a light sensor receives the beam, detects changes in opacity, and sends a proportional signal to the electronics unit. The wide-beam light source and narrow-view receiver make installation easy. Alignment of the breeching units does not need to be precise. The electronics produces a digital readout of percent opacity. SPDT contacts are provided for a remote alarm
After actuation, the alarm must be reset manually. The electronics unit is available in surface-mount and flush-mount styles. It can be installed in any dry, convenient area within 250 feet of the light source and receiver units. The face of the unit has a liquid crystal display and a “burner status” LED.