Electric control system with mechanical interlock

An electric control system for switching between supply lines extending to a load, comprising an isolation switching structure, a transfer switching structure, and a bypass switching structure;

• the isolation switching structure including first and second control devices, the transfer switching structure including third and fourth control devices, the bypass switching structure including fifth, sixth and seventh control devices, all of the control devices having contact carriers operable between open and closed circuit conditions;
• an emergency supply line including a first of two parallel paths extending to a load with one path including the first, third, and sixth control devices in series and with the other path including the fifth control device;
• a normal supply line including a second of two parallel paths extending to the load with one path including the second, fourth, and sixth control devices in series and with the other path including the seventh control device;
• and the bypass switching structure including interlock means including levers between the fifth, sixth, and seventh control devices for preventing closing of two control devices when one is previously closed.