The Simplex 4100-5401 ES-PS Power Supply Module is a primary system power supply designed for Simplex 4100ES addressable fire alarm control units. It provides regulated system power, battery charging, auxiliary outputs, and expansion capability for compatible option cards installed in the control panel.

The module operates from a 120–240 VAC input and converts power to regulated 24 VDC for the fire alarm control panel and connected field devices. It also includes a dual-rate, temperature-compensated battery charger capable of charging sealed lead-acid batteries up to 110 Ah when used with an external battery cabinet.