Safety relays are a very important element in the construction of electrical circuits and machines. They are designed to connect and disconnect power from the actuators in a hazardous situation. It is necessary to use at least two internal relays in the devices, otherwise they will not be considered safe and thus approved for use. Monitoring relays are compact voltage monitoring devices. They protect receivers against supplying electricity to them with incorrect parameters. This device, thanks to the wide range of modes, delays and settings, can be used wherever it is important to maintain high quality of the supply voltage.