System Sensor M500X Fault Isolator ModuleThe System Sensor M500X Isolator Module is an automatic switch that opens when the line voltage 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. Mounts directly to 4 square electrical box with a minimum depth of 21 8".