The system consists of a interface unit, which is connected to an optical fibre. The control unit sends a coded pulsed light through the fibre. The signal is received by the control unit and is compared with that sent out. Monitored devices are connected to the fibre via specially designed brackets or through  existing vents or similar in the monitored device. The control unit is connected to a 24-hour loop in the control panel and any attempt to remove a device or sabotage the optical fibre will generate an alarm.

The fibre allows the monitored device to be used in a normal way and the system is completely insensitive to electronic interference. The optical fibre is soft and about 2 mm in diameter, which makes it easy to bend. Maximum length of the fibre is 40m, which allows many devices to be monitored from one control unit.

The control unit has a relay output (NC) that can be programmed to latch or auto reset mode. The relay can be reset remotely via an input in the latch  function. The LED indicator can follow the relay or solely function in day-mode.