A power supply unit (PSU); a power converter that supplies direct current voltage to computer components. These units designed specifically for use with 110 or 230 volt alternating current (AC). Others can switch between the two or accept any voltage within that range. They also provide varying levels of direct current voltage, typically ranging between 3 and 12 volts DC.

They are ideal for controlling beam detectors, auto-dial communicators, aspirating smoke detectors, electromagnetic door holders, ventilation systems and more. Non-EN54 certified 12V and 24V PSUs are available for non-mandatory fire and other life safety applications. Switch-mode power supply unit offer low current consumption, deep discharge battery protection, single pole volt-free changeover relay, battery impedance monitoring