Not all transformers are equal. This Transformer features an easy-to-install lock mount or wall mount that can reduce installation time by 25%. An additional unique feature is the thermal cut-off switch designed to shut off the door chime system in the event of excessive temperature. NuTone saves you time and money! 8-volt, 20VA, 16-volt, 20VA; or 24-volt, 20VA transformer for use with multiple door chimes in one home; order in the standard package of six to help assist with your planning and still retain that economical edge. Quick install transformers, built to last so you should have fewer callbacks.