As an interface, interface relays connect the electronic control level, such as PLCs, with the level of sensors and actuators. They perform various functions: switching DC or AC loads with different resistive, inductive, and capacitive components, switching in a voltage range from a few mV to 250 V, switching in a current range from a few mA to 10 A, amplifying weak control signals, providing electrical isolation between control and load circuits, and signal multiplication. The CR-U series offers 12 different coil voltages with 2-3 changeover contacts. A built-in test button for manual operation and locking of the output contacts can be removed if necessary. Relays can be ordered with or without a built-in LED. Two socket variants are available: standard socket and logical socket. Plug-in function modules such as reverse polarity protection, flyback diode, LED module, RC circuits, surge protection, or multifunctional timing modules expand the application areas of the plug-in universal relays.