This is a Class D digital amplifier designed for commercial and industrial public address applications. Rack mount design in 1U type and rated power is 4*60W.Both balanced and unbalanced line inputs are available for each channel. Balanced line output feeds to another power amplifier as well as secures the signal transmission is less noise and longer distance. 70V, 100V speaker outputs are convenient for installation when selection different speaker matching. Complete protection includes clip, short circuit, high temp and overload. With indications for power, signal, clip, protection and temperature. This product can be called class d amp or 70v amplifier 4 channel.