This is my BeebMaster Econet clock. A device similar to this beats at the heart of every Econet. Very early BBC Micros with Issue 2 and Issue 3 motherboards had the space to have the clock circuitry installed directly onto the motherboard. Clocks were also built into Acorn Fileservers but later networks had separate clocks like the one below.
I have two of these clocks which I use in conjunction with my Econet Bridge to run two Econet network segments that run at different speeds with my 32-bit Acorn computers running on a fast Econet segment and my 8-bit Acorn comp