In the news.google this week is a press release for a clock that automatically tracks leap seconds. The PR glowingly touts how the clock traceable to NIST, so it is useful for timekeeping in all sorts of processes that need ISO 9000 certification. http://news.thomasnet.com/fullstory/488673 It goes on to say that the clock is always accurate to 1/10000 s.
The manufacturer has more to say http://www.control3.com/5125p.htm For less than $20 this battery powered clock is certified by an ISO 17025 calibration laboratory accredited by A2LA. But the only output is a liquid crystal display, and liquid crystals have response times around 10 ms. That's 1/100 s, not 1/10000 s. This seems akin to all the complaints about GPS receivers which display a time that is off by about 2 seconds. I've never bothered to dig on that, but my impression is that they probably also display a position of where they were 2 seconds ago. Finally, I've been spending a lot of time in the LA region lately. The CBS radio affiliate in the SF Bay area broadcasts the hourly national news spot on, and the time tone is useful for setting a watch. The CBS radio affiliate in the LA area very plainly is using a time compressing/FFT pitch shifting device on the live national feed. The time tone in LA always happens around 10 to 15 seconds after the hour. Sometimes system delay is unintentional, sometimes it is intentional. Even before PT Barnum latin had a two word phrase for such products. Somebody tell me again -- why is it thta broadcast civil time signals need atomic accuracy? -- Steve Allen <[EMAIL PROTECTED]> WGS-84 (GPS) UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99858 University of California Voice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m