This part of IEC 60947 specifies rules for control units, which perform the switching functions in response to the thermal detectors incorporated in rotating electrical machines according to IEC 60034-11, and the industrial application. It specifies rules for that type of system comprising a positive temperature coefficient (PTC) thermistor detector having particular characteristics, and its associated control unit. THIS CONSOLIDATED VERSION CONSISTS OF THE FIRST EDITION (2003) AND ITS AMENDMENT 1 (2006). THEREFORE, NO NEED TO ORDER AMENDMENT IN ADDITION TO THIS PUBLICATION.