4E1 PDH Optical Transmitter & Receiver is a photoelectricity syncretic transmission apparatus with 120 channels (be equal to 120 voice channels) . It takes GSI as core and provides E1 transmission which is suit to telecommunication. Offers 4 channels E1 ports, one channel RS232 and one channel service telephone. Supports full network management function. It adapts to switch group network of small capacity, loop network, mobile communication (base station) , special network, DDN and so on.Product Feature1. Adopts large-scale integrate chip, brief circuit, low power consumption and high reliability structure2. Offers four channels E1 ports, one channel RS232 and one channel service telephone3. Offers service telephone port for the convenience of installation and maintenance4. Possess the function of give a alarm by sound5. Provides one network management port, possess full concentrated network management function, convenient to configure the network and high security6. Possess complete alarm and state indication function7. Adopts manifold power supply: -48VDC or 220VAC