In a lighting system in which each of a multiplicity of lighting fixtures has a receptable containing a multiplicity of electrical contacts, a switching cable assembly is provided. A pass-through power plug of the assembly has a housing, a stem connector projecting from the housing with a multiplicity of electrical contacts adapted to mate with complementary contacts in the fixture receptacle, a power-in receptacle mounted in the power plug housing and a power-out receptacle mounted in the housing, and electrical conductors electrically connected, mediately or immediately, to and between contacts of the power-in receptacle, contacts of the power-out receptacle and contacts of the stem connector, the stem connector and its complementary fixture receptacle constituting the means for mounting the plug on the system. A switch cable boss in the housing accommodates electrical conductors electrically connected to the electrical conductors between contacts of the power-in receptacle and contacts of the stem connector.