As with the Acorns predating the BBC Micro, the first Econet Clock when the BBC was introduced formed part of the Econet interface on the BBC motherboard. This held for issues 2 and 3, but the BBC Econet interface was redesigned for issue 4 to remove the Clock and termination capability.

The picture above shows an Issue 2 BBC Model B which has the Econet interface fitted, but not the Clock circuitry, which would be added to IC 90 and IC 92, with a bank of link jumpers fitted to S3 to set the Clock speed in kilohertz.