The PRISM power supply chassis provides a distributed network of DC supplies. Each chassis contains 2 × 500VA monitored DC supplies.Primary power is derived from a 230 volt AC 50Hz supply, which is transformed and rectified to provide a + 24 volt DC supply. This supply, rated at 10 Amps RMS, is distributed via independently fused outputs to an appropriate number of amplifier chassis depending on amplifier loading. In addition, the supply is regulated and used to charge the secondary supply standby batteries. This secondary supply is used in the event of primary (mains) failure, and is supplied with sufficient capacity to meet the specification, 24 hours standby + ½ hour with tone and message into system load.