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 Feature 1. Adopts large-scale integrate chip, brief circuit, low power consumption and high reliability structure 2. Offers four channels E1 ports, one channel RS232 and one channel service telephone 3. Offers service telephone port for the convenience of installation and maintenance 4. Possess the function of give a alarm by sound 5. Provides one network management port, possess full concentrated network management function, convenient to configure the network and high security 6. Possess complete alarm and state indication function 7. Adopts manifold power supply: -48VDC or 220VAC