PRO1323 4-ZONE AUDIO POWER AMPLIFIER INTEGRATED 4 SOURCE STEREO PRO2 A-1323Overview PRO1323 PRO2 4 ZONE AUDIO POWER AMPLIFIER With a diverse range of inputs, including digital (optical or coaxial) and dynamic microphone inputs, and the ability to adjust each zone's volume independently, the PRO1323 is a quick and easy way of adding audio in up to four rooms. It also features a Loop out for expanding to another unit, increasing the number of zones further. Four in and five out IN: 1 Digital (Optical Coaxial selectable), 1 RCA