Suitably used in bi-directional transmission (can be reserved) and signal equalization of multi-class trunk transmission or high-required distributive network. Adopt PHILIPS, MOTOROLA imported power doubler module. Audio pre-amplifier is low-noise microwave tube push-pull amplifier to insure enough gain. It has 1 input and 2 outputs, and each connection has over-current protection. The ouput branch or distributiveness can be changed following it. Double-equalizer is used, so adjusting multi-class transmission flatness is simple and convenient. Attenuator and equalizer are plug in, so customers can choose fived or adjustable style. High-reliable switch power (or linear power) and strict waterproof and anti-thunder design insure steady durative work.