A sensor usually contains a receiving (sensing) member, as well as one or more intermediate converters. However, the sensor frequently consists only of the receiving member (for example, a thermocouple, a resistance thermometer, or a strain gauge). The output signals of a sensor are distinguished according to the type of energy (electrical, mechanical, pneumatic, or less frequently, hydraulic) and the type of modulation of the energy flow (amplitude, frequency, phase, or discrete [coded]).