Abstract: A monitor system is described which is capable of providing an output which indicates the oscillatory torque in each section of a multi-section shaft of a rotating system having plural masses. The system described is an electronic model of a mathematical analog of the rotating system and is based upon the assumption that the system may be represented as N inertias or masses interconnected by N-1 shafts -- represented as springs. For such a system there are n-1 primary frequency oscillatory torques. If the inertias are large, the frequencies of these torques are low. Electrical signals representing the torques are sensed at one or more shaft sections and are filtered, amplified, passed through a plurality of weighting network and recombined to provide an indication of the total oscillatory torque in each of the N-1 shaft sections. Such torque, or an electrical output signal from a generator, in the instance of a turbine-generator set may be used to actuate an operative means or actuate a system alarm.