USHK-04 loop monitoring device

The device USHK-04 is intended for use in four-wire loops of security and fire alarm system as a terminal relay of voltage presence in the supply line. The main element of the UShK-04 circuit is an optorelay. The input circuit of the optorelay is supplied through a noise suppressing filter. An optical indicator of yellow (green) colour is connected in series with the input circuit of the optorele. In the output circuit, in series with normally open contacts, a resistor (24 Ohm) is included to protect the optorele from erroneous connection of the output to the power supply circuit.