Battery or mains powered versions available.
Simple operating principle; Float switches are suspended inside the top of the tank and inside the bund. These are factory attached to the alarm with cables of 2m in length. Once the level of fluid in the tank or bund raises the float, an audible alarm will sound.
Now, also available, a 230V mains version with Volt Free (VF) contact on Bund (Order VF version).