On 05/08/2017 14:34, Chris wrote:

Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.

Untrue.

The matter starts off when the slave signals to the master and drops
the gravity link in the master, then, when the master pendulum is in
a position to accept the impulse from that dropped gravity link, it
signals back to the slave

But ... I'm still trying to google for the exact mechanisms because
most URLs only hint at what is happening. (I'm also awaiting delivery
of a couple of hope-jones' books about electric clocks)