EVA - UB4 Standard Base is a 4 inch mounting base for Nittan's UL listed detectors that can be mounted to 3-1 / 2 inch octagonal electrical boxes . The base contains no electrical circuit so that the base is used as a terminal block . The base is supplied with 4 terminals that are used depending on the detector heads . The 12-20 AWG field wire can be connected to the terminals . EVA - UB4 contains a locking screw to avoid unauthorized removal of detectors .