PDH (Plesiochronous Digital Hierarchy) which was used in exchanger for long distance transmission, and platform of mobile telecommunication, pager transmission station ect., which was used in mini-medium column and point to point products with fiber supporting, the equipment adopted powerful function and expert digital repeating-connection chips which integrated all digital and logical function in the equipment so that improved the performance and reduced the cost of products, the completed-equipment with good performance, stable operation, low loss, strong integration capacity, small bulk, easy installation and maintenance.