10BASE5 (also known as thicknet) is the original "full spec" variant of Ethernet cable, using RG-8 (Radio Grade - 8) coaxial cable. A stiff, large diameter cable with an impedance of 50 ohms and with multiple shielding. The outer sheath is often yellow polyvinyl chloride so it frequently is just called "yellow cable". The name 10BASE5 is derived from several characteristics of the physical medium. The 10 refers to its transmission speed of 10 mbit/s. The BASE is short for baseband signalling as opposed to broadband, and the 5 stands for the maximum segment length of 500 metres.
10BASE5 cable is designed to allow transceivers to be added while existing connections are live. This is achieved using a vampire tap - a device which (with sufficient practise) clamps onto the cable, forcing a spike through the outer shielding to contact the inner conductor while other spikes bite into the outer conductor. This is often built into the transceiver and a more flexible multi-wire cable carries the connection between the transceiver and the node.
The maximum practical number of nodes that can be connected to a 10BASE5 segment is limited to 100 and transceivers may only be installed every 2.5 meters. These suitable points are marked on the cable with black bands. The tranceivers connect to nodes using a DB-15-style connector (identical in appearance to a joystick port) called Attachment Unit Interface (AUI).
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Last updated: 10-14-2005 03:58:36
