It should be noted that the relays consist of elements considered essential for the execution of maneuvers of electric charges, since they allow the combination of logic in the command, in the same way as the separation of the power and command circuits. The simplest types of relays are formed by a housing with five terminals. The first two terminals correspond to the excitation coil. The third terminal is the input terminal gfm20a hubbell wiring , and the fourth and fifth terminals correspond to the NC contacts, normally closed, and NC, normally open, respectively.
Thus, an important specification of the relays to be considered is that the voltage at the first two terminals can be 5 Vdc, 12 Vdc or 24 Vdc, at the moment simultaneously terminals three, four and five can operate with 110 Vac or 220 Vac. In this way, there is no physical contact between the drive terminals and the work terminals. This process allows the existence of two circuits in an electrical panel. One is the control circuit, in which the interface with the operator of the machine or device is found, working with low currents and / or low voltages. It is in the power circuit where the loads to be driven are located, as well as motors and heating resistors, among others.