Same physical topology as ThinNet but different.
As Known as 10Base5.
The proper ThickNet cable is coloured yellow and is around 8mm in diameter.
It is a heavier cable and it's minimum bending radius is no more than 100mm Radius.
Because of these physical constraints, it is not directly terminated on any of the equipment.
It is terminated via a special cable clamping and termination arrangement knowns as a "Vampire Tap" and a transciever is mounted on the "Vampire Tap", the drop connection to the equipment is done using an AUI cable.
Each end is terminated with a 50 ohm terminating resistor and one end is earthed.