1. PDH fiber optical multiplexer ,4E1 2.rs232,service telephone 3.reasonable price,swift delivery PDH fiber optical multiplexer HS-OPT series PDH optical multiplexer ,which is based on super large scale integrated circuit ,a point to point ,link circuit ,loop optical transmission equipment . It can supply 4/8/16/24 interfaces ,one channel 100M ethernet interface ,one channel order wire phone , ...