RG8
<networking, hardware, cable> (Or "thicknet" - "thick
Ethernet") The original "full spec" cable, used for
10base5 Ethernet networks.
RG8 is stiff, large diameter coaxial cable with an
impedance of 50 ohms, a member of the "Radio Guide" series.
The outer sheath is usually yellow, to indicate double shielding, so it is often just called "yellow cable".
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.
RG58 is a cheaper, more flexible alternative.
