Hi,

I was referring to a list of hardware or software that will provide time.

Al

On 1/16/06, Rob Kimberley time.bandit@btinternet.com wrote:

Alan Kruse wrote:

My 19th century French clock provides the time !! No software needed.

My computer, made by Sun, has a built in clock too.

You need to be a bit more precise about what you want.

Alan Kruse wrote:

A clock consists of a frequency standard plus a counter.  Accordingly, a
list of "hardware" that provides time would include:

A. Mechanical wrist watches and mechanical clocks. For these, the
frequency standard might be a pendulum, and the the counter might be an
arrangement of gears to count seconds, minutes, houts, etc., and display
them on mechanical dials for the user to observe.

B. Electrically powered wristwatches and clocks that include tuning
forks as their frequency standard.

C. Electrically powered wristwatches and clocks that include crystal
oscillators as their frequency standards.  Most retail clocks and
wristwatches fall into this category.

D. Wristwatches and clocks that include crystal oscillators that are
"synchronized" from time to time with radio receivers. These include,
for example:

D.1. "Atomic Time" and other brands of wristwatches and clocks that
synchronize their dials (counters) against the 60 kHz LF signal from
WWVB near Ft. Collins, Colorado.

D.2. Similar products that synchronize their dials against other LF
signals from other LF (low frequency) or MF (medium frequency) time
signal stations such as MSF (Rughy, United Kingdom, 60 kHz); TDF
(Allouis, France, 162 kHz); HBG (Prangins, Switzerland, 75 kHz); etc.

D.3. Similar products with HF radio receivers for such time and
frequency stations as WWV (Colorado, USA: 2.5 MHz, 5.0 MHz,  10.0 MHz,
15.0 MHz, 20.0 MHz), WWVH (Hawaii, USA: 5.0 MHz, 10.0 MHz, 15.0 MHz),
CHU (Ontario, Canada: 3330 kHz, 7335 kHz, 14670 kHz), BPM (Shaanxi,
China: 2.5 MHz, 5.0 MHz, 10.0 MHz, 15.0 MHz), etc.

D.4. Similar products that both "synchronize" their counters and
"syntonize" their frequency references against standard time and
frequency broadcasts.

D.5 Similar products that either "synchronize" their counters (or both
"synchronize" their counters and  "syntonize" their frequency standards)
against signals received from GPS satellites.  Almost any GPS receiver
will display time of day.  (Many will not, however, display it in a
"timely" manner!)  GPS receivers that are to be used for precise timing
purposes should provide a 1 Hz (1 pulse per second) output.  Some of the
better ones will provide 5 Hz or 10 Hz outputs, if they provide fixes 5
or 10 times per second.

As Rob Kimberly said, a list of hardware timing devices could be rather
lengthy! It would help if you could be more specific, and perhaps rule
out such devices as mechanical clocks and chronometers.

--
James Maynard
Salem, Oregon, USA

Hi James:

Astronomical methods, such as sundials might deserve a place on the list.

73,

Brooke Clarke, N6GCE

--
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

On Mon, Jan 16, 2006 at 03:14:44PM -0800, Brooke Clarke wrote:

Absolutely.  Over the long term, these are often the most accurate,
where the periodic motion of some astronomical body provides a
frequency source, and humans do the calculating and counting.

That is certainly true historically, where observations of the
positions of the sun rise/set on the horizon, observations of the
positions of moon and planets, eclipses of moons of jupiter, etc
provided the definition of time until recent decades.

And it is still the case that an independent check on our atomic
clocks by counting pulsar pulses is very valuable input.  As I
understand it, astronomical observations contributed to the steering
of the frequency rate of TAI, possibly as recently as 1977 and 1995

on 1977-01-01 the rate of TAI was reduced by one part in 10^12

In 1995 a CCTF working group determined that the length of TAI
seconds was longer than the SI second because the clocks contributing
to TAI were not corrected for the effects of blackbody
radiation. Over the next three years the frequency of TAI was steered
to reduce the length of its seconds by about 2 parts in
10^14. Therefore the length of UTC seconds was also reduced. This
change is evident as the final kink in the plot of TT(BIPM04).

See http://www.ucolick.org/~sla/leapsecs/timescales.html

And if you want a device that is intended to work for a LONG time,
see

http://www.longnow.org/projects/clock/

The 10,000 Year Clock
The idea to build a monument scale, multi-millennial, all mechanical
clock as an icon to long term thinking

Two prototypes now exist, and work continues.

Finally, clearly a computer can function as a clock, as originally
pointed out, but missing from James' list.

=> D.6 Devices that synchronize with the NTP or SNTP protocol.

Cheers,

Neal McBurnett                http://bcn.boulder.co.us/~neal/

Brooke Clarke wrote:

Indeed.  Sundials, or menhirs, such as those at Stonehenge!

However, on re-reading the original poster's request, I see he was look
for "time synchronization" hardware or software. To qualify, I think
such hardware ought to provide for performing the synchronization
function -- such as, for instance, outputting a one-pulse-per-second
signal at its estimate of the exact UTC (or TAI) second boundary.
Otherwise, the equipment would be a clock, but not "time synchronization
hardware."

--
James Maynard
Salem, Oregon, USA

James Maynard james.h.maynard@usa.net wrote:

Even better, pulsars. They have a period that is usually the same order
of magnitude as a second, and some of them are regular enough that they
are similar in stability as an atomic clock (how many of us have
cesium beam tubes that will last for billions of years, hmmm?)

Tim.