Each unit provides two independent power converters with current and over voltage protection circuits, improved monitoring of charger and all DC outputs to ensure reliability.

The power supply provides two individually protected outputs at 24V to feed either two BV220, two BV120D or one BV440M power output modules. In the event of mains failure power is maintained using an external standby battery which is continuously float charged by the charger section of the PSU unit.

The unit has built-in deep battery discharge cut off; this prevents total discharge that can destroy the standby batteries in the event of AC power failure for any long periods.

A third protected output is provided to power a mixer or auxiliary circuits. All these outputs, together with a fault volt free changeover contact, are provided by a nine-way crimp connector plug and socket.

The charger section is totally monitored and indicators for AC supply healthy, fuse failure, charger fail, battery voltage high, and battery voltage low are incorporated. Should any of the above fault conditions occur, an internal relay releases providing a changeover contact, signalling to the control system. The charger incorporated is of the constant voltage type set for the recommended float charge.

Should the battery be below this float charge it will charge in a constant current mode at the rate of three amps and progressively reduces once the battery has achieved its nominal float level. Several chargers may be paralleled when used for larger systems and must be synchronised.