The Maxiswitch 2-way control unit is used for switching HID lights on and off. A controller is a core component of your grow-room as segmental timers alone will not handle the electrical load demanded by HID lights.
The unit works by diverting the live load around the segmental timer to a contactor/relay, the timer simply switches the contactor/relay to complete/break the circuit. This 2-way unit is rated to 10A, it will switch up to 2 x 1000W grow lights (1000W grow lights draw 5A each in use).
The controller has two UK plugs running from it; one plugs straight into the wall-socket, one plugs in through the segmental timer which dictates the light cycle.