To provide a switch having overcurrent and undervoltage functions for an electric protection device.

This switch has a mechanical switching contact 2, a switching latch 6 capable of latching for the make-and-break contact 2, an overcurrent sensor 3 linked with conductors S1-S3, and an electromechanical undervoltage relay 7, the switching latch 6 which are released when they are in excited conditions. The overcurrent sensor 3 separates the undervoltage relay 7 from an exciting voltage in the case of overcurrents, and drops in the case of undervoltages. Thus, in both the case of overcurrent and undervoltage, the release of the switching latch 6 is effected by the undervoltage relay 7. A particularly simple current transformer for obtaining currents flowing in the current conductors S1-S3 is formed by a pair of induction loops on both sides of each conductor cross section on a printed circuit board, and opposite pairs of iron core halves K11-K32 are provided, in such a way that one of the halves of each pair is located on each side of the printed circuit board.