Automatic standby units are designed for fully automatic control of standby of two power supplies. They also allow for manual mode, when the power supplies are switched by operator. In case that the standby power supply, they can perform the standby in 3 seconds. Modeion compact circuit breakers or Arion air circuit breakers are used for switching of power supplies. Automatic standby units thus cover applications from 16 to 6 300 A.