PURPOSE: To obtain a controller capable of automatically discriminating a kind and a size by connecting one wire or two single wires on a single wire side and a double-wire side to a joint having the connector pins to an electric heating wires arranged to both end parts thereof by one and connecting two wires on the double-wire side to a joint having two connector pins arranged to the single end part thereof.

CONSTITUTION: The single wire plug 24 and the single port 26A of a double-wire plug 26 provided to the leading ends of the electric cords of the cables 21, 25 provided to a controller 20 are inserted in the connector pins 13A, 13B provided to both ends of a socket 11 to be connected thereto. When minute voltage is applied, a minute current flows across the electric cords 21, 22 and, therefore, connection is cleared and it can be discriminated that the joint thereof is a type welded to both sides of a socket type at the same time. By measuring the current flowing to a joint electric heating wire 12, the size of the joint is also discriminated. Thereafter, the current supply button of the controller 20 is pushed, the optimum quantity of electricity preset at every joint size is automatically controlled to be supplied to the joint.