An electronic device which enables input signals to control a local source of power and deliver output signals of greater amplitude with respect to current and/or voltage. the output signals characteristics are uniformly related to the input signals, and are suitable for controlling or supplying power for exciting electric motors or similar devices. it includes devices commonly referred to as servo amplifiers, torque amplifiers and similar equipment only if these devices do not employ synchros nor incorporate servomechanisms. it does not include items which are properly classified as audio frequency, radio frequency, direct current or video amplifiers. for amplifiers that incorporate servomechanisms and employ synchros, see amplifier, synchro signal.