The PEM7D is a compact entry and approach warning system for
use in shops, reception areas, private homes, etc. It is a
self contained photoelectric beam and sensor unit, which
works by sending out a beam of infrared light, bouncing it
of a reflective disc and receiving it on sensor. If the beam
is interrupted i.e. when a person walks through it, an alarm
is triggered and an audible warning sound can be heard. The
time the alarm is on and the volume or both easily adjusted.
