I think there was also an "Accutron" clock movement that could be driven from 60kHz. I think this movement was in at least some HP timekeeping instruments. In any event those were not truly silent either... put an Accutron up to your ear and you hear a high-pitched hum/buzz, not tick-tick-tick. -----Original Message----- From: Shoppa, Tim Sent: Tuesday, February 26, 2013 4:26 PM To: cctalk at classiccmp.org Subject: Re: OT: WWVB clock with silent movement Various "time-nuts" start off with GPS disciplined rubidium clocks, or radio clocks like WWVB, and derive a phase-locked 60Hz to run the old-fashioned 120VAC continuous-hand-movement analog and flip clocks (in my circle known as "NUMECHRON"s although I think the most applicable trademark was TYMETER). One example is: http://leapsecond.com/pages/atomic-nixie/ Obviously an HP 3325B is overkill as a 60Hz synthesizer but you get the idea. If you have WWVB carrier, 60Hz is just dividing by 1000, no funny numerator/denominator stuff.