Panel and plural module assembly having mechanical keying and modular plug structure to activate/deactivate automatically bridged load carrying circuits

A modular switching and control system comprising;

• a. a master structure;
• b. a plurality of independent switching and control units;
• c. said independent switching and control units being of at least first and second different types;
• d. said master structure containing mechanical means cooperative with means on said switching and control units for mounting said switching and control units in and removing them from said master structure;
• e. said mechanical means being of at least first and second types and having means for preventing mounting of at least said second type of switching and control unit in said first type of mechanical means;
• f. a plurality of first electrical connector plates in said master structure;
• g. a second electrical connector plate on the rear of each switching and control unit, said second electrical connector plate being adapted to electrical and mechanical mating with at least one of said first electrical connector plates in said master structure;
• h. means in each said first electrical connectors which is associated with an external load carrying circuit for maintaining power to the external load carrying circuit when its associated second electrical connector is withdrawn;
• i. means in each said second electrical connector which is associated with an external load carrying circuit for interrupting said means for maintaining when said second and first connectors are mated;
• j. a test connector on at least one switching and control unit said test connector being accessible from external to said unit;
• k. a test plug having terminals adapted to mating with said test connector;
• and
• l. means on said test connector and test plug for making electrical connections with circuits within said switching and control unit.