On 01/08/17 12:00, Gareth's Downstairs Computer wrote:
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...

http://www.meccanotec.com/shortt.html

While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then
use use used to 'pull it' to reduce the error- which is how a true phase
lock loop works.

The system seems to operate more as follows, the slave is designed to
run 'very nearly right'. It receives precise pulses from the master
which it will naturally sync to. The same will happen if you have two
oscillators on nearly the same frequency if you 'feed' the output of one
to the tuned circuit of the other. (Including harmonics.) This is used,
for example, by some amateurs to lock radio oscillators to GPS locked
references.

Still, it is an clever system and of interest.