The SK-ISO is an addressable line isolator module for use with the Honeywell Silent Knight Series fire alarm control panels (FACPs). The SK-ISO acts as an automatic switch that opens when the line voltage on the signaling line circuit (SLC) loop drops below four volts. Isolator modules should be spaced between groups of sensors or modules in a loop to protect the rest of the loop. If a short occurs between any two isolators, then both isolators immediately switch to an open circuit state and isolate the devices between them. The remaining units on the SLC loop continue to fully operate. No more than 25 devices are recommended for each group.