Home Lighting Control (HLC) is for single phase 120/240-volt, 60-Hz systems. The HLC Phase Coupler mounts by the circuit breaker box and is used to connect the signal from L1 to L2 within the circuit breaker box. Although HLC is extremely robust and less susceptible to powerline conditions, Leviton recommends the use of a Phase Coupler in every HLC installation. The Phase Coupler increases the speed and reliability of the entire system.