It is suitable for use in multi-class trunk transmission to compensite or strict distributing network. Pre-class adopted low-noise microwave tube double-class push-pull amplifier insure enough gain. Mainoutput and bridge output are both adopted push-pull module amplifier 1 input and 2 output have over- current protection (fuse plug-change). Branches or distributers at output can be plug-changed freely. Adopt fore and ATT double Equalizer to adjust flatness sensitive and convenient. Import double layer PCB a high reliable linearity power and a multi strict anti thunder system are set. All these insure long live and safe work.