T1/E1/J1 Dual Connector Interface


Application Note 384 describes how to connect the Dallas Semiconductor 3.3V Line Interface Units (LIUs) and Single Chip Transceivers (SCTs) to a network interface that contains both BNC and RJ-48/Bantam type connectors. In telecommunications designs, BNC connectors use coaxial cable and RJ-48/Bantam connectors use twisted-pair cable. While the coaxial cable uses the center conductor to carry signal information and the outer shield is connected to ground, the twisted-pair cable uses both conductors to carry signal information. Any design that supports both interfaces usually needs jumpers or switches to choose between the two interfaces. Using a transformer with a dual secondary winding allows the design to support both interfaces without the use of switches and jumpers. One secondary winding is routed to the BNC connector and the other winding is routed to the RJ-48/Bantam connector. The end user then chooses the appropriate interface by simply connecting a cable to the appropriate connector and does not have to worry about jumper or switch settings.