The voltage monitoring relay UB A400 opens auxiliary load circuits when battery voltage becomes too low and restores them when voltage recovers. A 20-second delay precedes opening a load circuit, and a 2-second delay precedes restoring it. The plug-in design offers a secure locking feature for maximum ease of maintenance, with no wires to disconnect for inspection or replacement. Resistance to impact and vibration conforms to railway equipment standards, with positive mechanical keying and clearly marked terminals. The UB A400 plugs into the EA 102 B and compatible B-type sockets.