First we can classify Electromagnetic relays according to the nature of the intermediate signal between the main side and the switching element. The magnetic field generated by the input signal acts on the mechanical contacts. Examples include standard yoke type relays and reed relays. This standard yoke type relay consists of a coil, armature and one or more sets of contacts wound on a soft iron core. When current is applied, the coil generates an electromagnetic field and the armature is activated. The armature is the moving part of the relay. It is hinged on a yoke, mechanically connected to the moving contacts, opens and closes the contacts, and has an additional spring that returns it to its original position. The armature is held in place by a spring, so when the relay is de-energized, there is a gap in the magnetic circuit. While all versions offer the same basic operating concept, electrical relays use slightly different technologies and come in a wide variety of sizes and types.

Electronic relays use electronic switches (such as transistors, triacs) as the main switching element. This allows the relay to control larger circuits. Other types of electronic relays (transmitting by means of optics, frequency modulation, or capacitive effects, etc.) include optocouplers (on the main side, the light signal is transmitted through a light-emitting diode, while a phototransistor acts as a receiver and controls the switching element), thermoelectric relays ( The main input energy heats the bimetal parts, mechanically drives the contacts) and piezoelectric relays (piezoelectric effect mechanically operates the contacts). Electromagnetic relays are widely used in aviation, aerospace, ships, home appliances and other fields. They mainly complete functions such as signal transmission, execution control, and system power distribution. They are one of the key electronic components in each system.