The PB 1000 Series Audio Power Amplifiers are completely engineered with the latest advancement in audio technology. Vast improvements were made to the sonic performance and operation stability with current protection circuitry. The power amplifiers provide wide frequency response, low THD level and high S/N ratio. The PB 1000 Series is also incorporated with toroidal transformer technology which reduces electromagnetic noise and improves power efficiency. The audio power amplifier features 2 inputs; Program Input and Priority Input. The Priority Input which is used during emergency paging will automatically override the Program Input, normally used for announcements and background music. All models can operate on both AC mains power or a backup 24 Vdc power source, providing continuous uninterruptible operation even during a power failure.