583,716. Automatic circuit-breakers. WEST & CO., Ltd., A., and PAVITT, F. J. Nov. 21, 1944, No. 23133. [Class 38 (v)] In a protective relay especially of the construction described in Specification 549,521, an upright arm 53 pivoted at its lower end at 54 extends up between two of the coils 1 and engages the rear end of the tripping plate 22 when the latter is in its normal position The arm 53 is biassed by a spring 55 so as to move to the position shown in dotted lines subsequent to the raising of the tripping plate 22 on the occurrence of an overload or underload. Contacts 51, 52, one of which is carried by the arm 53, are opened by movement of the latter and interrupt the circuit of a winding 7 of a main switch, causing the magnet frame 32 to fall and open the said switch. As the magnet frame falls it bears on an arm 56 rigidly fixed to the arm 53 thereby automatically returning the latter to its former position, where it is again held by the plate 22 which is also returned to its normal position in response to the opening of the main switch. Manual-opening of the main switch may be accomplished by a push rod 58 acting on contact 52. The arm 56 is made detachable in case automatic resetting is not required.