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.
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