TC70 is a specialized device for monitoring and protection of 3-phase asynchronous motors, designed for DIN-rail mounting. It monitors phase presence and order, phase line voltage, and zero presence, and switches off its relay output in the cases of failure. An additional input for connecting a thermistor with positive temperature coefficient (posistor) is used for monitoring motor temperature. A cheap, yet highly reliable device, TC70 can be used not only for motor protection, but also in all cases, in which 3-phase system power supply should be monitored.