Hi, I'm aware of European systems who run the seconds of a 'slave dial' on 220 Volts 50Hz, the seconds hand makes one full revolution in about 59 seconds and then stops till the Masterclock provides the 1 minute pulse @ 24 Volts DC, which releases the brake and the process starts all over again. This will keep the seconds hand in step with the master clock.
Minute pulses are positive , negative, pos. etc to prevent a clock jumping 2 minutes in case of contact bounce from the master.
In the drive from the synchronous motor to the seconds hand is a slip clutch provided which avoids stalling the motor.
Many railwaystations in The Netherlands and Germany use these types of clocks ( T&N and FAVAG ) The seconds hand makes a smooth pulsing movement and stops briefly at each second. "schleichenden sekunden".
In the Simplex system I think that a similar approch is used mains voltage for the motor and 24 Vdc for the minutes although not with changing polarity.