In the Standard Electric Time Company slave clocks that I've got, the master sends about a 12ms pulse once a minute, which pulls in a solenoid and allows a leve

In the Standard Electric Time Company slave clocks that I've got, the master sends about a 12ms pulse once a minute, which pulls in a solenoid and allows a lever to ratchet one tooth on the minute wheel and advance the movement. Then once every twelve hours, the master sends a longer pulse, which pulls in a stronger second solenoid that allows the wheel to turn freely. There's a weight on the hour wheel which will pull the wheel around until the weight is on the bottom because of gravity, which corresponds with 12 o'clock. So no matter where the clock is, it will fall back to twelve with the longer pulse, and then begin the ratcheting again with the once a minute shorter pulses. (Sorry for the deprecated master/slave terminology, it's unfortunately what they used at the time)