3.2 10BASE5 Components
The specifications state that there may be a maximum of 100 MAUs attached to a segment, and that each MAU connection to the thick coax be placed on any one of the black bands marked on the coaxial cable. The black bands printed on thick coaxial cable provide connection points that are spaced a minimum of 2.5 meters apart. The minimum spacing and the restriction on the number of MAUs are both designed to limit the amount of signal attenuation and distortion that can occur on a given cable segment.
The most popular attachment mechanism (MDI) for a 10BASE5 MAU is sold by AMP Corporation, and consists of a metal and plastic clamp that makes a direct physical and electrical connection to the coaxial cable. This clamp is also called a transceiver tap, since to install the clamp you must drill a hole into the thick coaxial cable in a process known as tapping the cable. Since this clamp may be installed while the network is active, it is also called a "non-intrusive" tap.
Another, much less popular, form of thick Ethernet MDI consists of a tap composed of two type N coaxial cable connectors. Installing this tap requires cutting the thick coaxial cable, installing N connectors on each cable end, and then installing the tap as a type of "barrel" connector in-line with the coaxial cable. Cutting the cable halts the operation of the network, earning this approach the label of "intrusive tap."
The external MAU is equipped with a male 15-pin AUI connector that has two locking posts, providing an attachment point for a sliding latch connector. The MAU is powered from the Ethernet interface. The specifications state that a MAU may draw as much as 0.5 AMP (1/2 AMP) of 12 volt DC power.
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