In our SDH or packet network with TDMoverPackets we have the traditional 2 Mbps E1 service. It uses the HDB3 line code which is a code used for baseband transmissions between telecommunications devices. The HDB3 code has the following characteristic: high clock extraction capability, no DC component, error checking capability, and a maximum of three consecutive zeros.
The tool can be easily made with an LED, an amphenol connector, a soldering iron and tin, in order to quickly detect a fault in our 75 ohm DDF. I leave you the figures they speak for themselves.
We will only have signal in the connector with transmission. If the port has service, we will have a signal in the two connectors through the TX signal of the transmission network element and the TX signal of the client equipment. If the port is free without a client, we will only have a signal in the TX. I leave you a port in loop without service so that you can draw your own conclusions.
