All detectors in the Series 65A range fit into Series 65A mounting bases. The bases are of four or six inch diameter and have five terminals. Detectors are polarity insensitive, so that identification of positive and negative lines is only required if a remote LED is fitted. Detectors fir into bases one way only and require clockwise rotation without push force to be plugged in, particularly useful when fitting to suspended ceilings. They can be locked into the base by a grub screw using a 1/16″ hexagonal driver. An earth connection is not required for either safety or correct operation of detectors. The earth terminal is provided for tidy termination of earthed conductors or cable screens and to maintain earth continuity where necessary. Bases have a wide interior diameter for ease of access to cables and terminals and there are two slots for fixing screws at a spacing of 2.01 inches (51 mm) to 2.72 inches (69 mm).