An interlock assembly for a bypass isolation open or closed transition ATS assembly is disclosed. The interlock assembly ensures that a switch assembly being worked upon and/or being inserted is in a neutral configuration, i.e. the switch assembly is not engaging a power source. The interlock assembly is, preferably, an electrical interlock having a control system structured to configure the switch assemblies and to monitor the configuration of the switch assemblies. That is, the switch assemblies each include a power operated, conductive, movable contact arm. The position of each contact arm is controlled, and monitored by, the control system which controls the single actuator for each contact arm.