Data Acquisition

cabling tray etc and the transceiver electronics (medium attachment unit, MAU) isinstalled directly on the cable. From there an intermediate cable, known as an attachmentunit interface (AUI) cable is used to connect to the network interconnection card (NIC).This cable, which can be a maximum of 50 meters long, compensates for the lack offlexibility of placement of the segment cable. The AUI cable consists of 5 individuallyshielded pairs – two each (control and data) for both transmitting and receiving, plus onefor power.The MAU connection to the cable can be made by cutting the cable and inserting an N-connector and a coaxial tee or more commonly by using a ‘bee-sting’ or a ‘vampire’ tap.The tee is a mechanical connection that clamps directly over the cable. Electricalconnection is made via a probe that connects to the center conductor and sharp teeth,which physically puncture the cable sheath to connect to the braid. These hardwarecomponents are shown in Figure 9.1.Figure 9.110Base5 hardware componentsThe location of the connection is important to avoid multiple electrical reflections onthe cable, and the Thicknet cable is marked every 2.5 meters with a black or brown ringto indicate where a tap should be placed. Fan out boxes can be used if there are a numberof nodes for connection, allowing a single tap to feed each node, as though it wasindividually connected. The connection at either end of the AUI cable is made through a25 pin D-connector, with a slide latch, often called a DIX connector after the originalconsortium.