100 Years of Synchronized Timekeeping 2-17

Transcription

100 Years of Synchronized Timekeeping 2-17
120 Years of Synchronized
Timekeeping in the USA
Ken Reindel
Director of Measurement Technology, NI
Founder, Ken s Clock Clinic and KCC Scientific
President, NAWCC Chapter 15
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What Is the NAWCC?
•  Founded in 1943, The National Association of Watch and Clock
Collectors, Inc. (NAWCC) is a nonprofit scientific organization that
serves as a unique educational, cultural, and social resource for its
membership and the public at large.
•  Members include hobbyists, students, educators, casual collectors,
and professionals in related retail and manufacturing trades. The
one common bond (and main membership requirement) is a
fascination with the art and science of timekeeping (horology).
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What is NAWCC Chapter 15?
•  Chapter 15 is the local Chapter of the NAWCC.
It is an active society of local participants with a
common passion around Horology.
•  150 members from Austin, San Antonio, Dallas,
Houston and surrounding areas
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What is the IEEE?
•  World s largest professional association
•  Dedicated to advancing technological innovation
and excellence for the benefit of humanity
•  Its mission is to inspire a global community
through IEEE's highly cited publications,
conferences, technology standards, and
professional and educational activities.
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Agenda
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A Brief History Lesson
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From 5000BC to Present Day: Defining Time
Time Standards, UTC
The Naval Observatory—Astronomical Timekeeping
WWVB Atomic Clocks and Cesium Atomic Clocks
Earliest Synchronized Time: The Self Winding Clock (1890-1960)
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Henry Chester Pond
Battery and Telegraph Technology
The Clocks
The Synchronizing Technology
•  The Partnership with Western Union
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The Power System: The Next Step (1928-Present)
–  Henry Warren
–  The Synchronous Motor, Clock and its Successors
–  Examples
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The Future
–  What is the status of NERC s experiment from July 2011?
•  Will the grid eliminate time correction?
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Brief History of Timekeeping
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Astrology vs. Horology
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A belief that the future can be told with stars has persisted for 5000 years
The Zodiac: Based on the Duodecimal system; eg, divided into 12 sections
–  Capicorn, Aquarius, Pisces, Aires, Taurus, Gemini, Cancer, Leo, Virgo, Libra,
Scorpio, Saggitarius
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Ptolemy of Alexandria (2 AD) first to suggest the earth was not the center of
the universe
–  Developed extremely accurate sky maps dividing sky into minutes and seconds
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Earliest complex mechanisms were models of star motion
Much can be learned of the history of Horology from the study of Astrology
(and later Astronomy)
http://www.praguealacarte.com/orloj/orlojLoader.html
Prague Astronomical
Clock ca 1380
12 Signs of Zodiac
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Units of Time Measurement
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Dates back to the Babylonians
–  Built on astrological observations
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A day was defined by Earth s full rotation
From Full Moon to Full Moon = 30 days
Spring equinox to Spring equinox = 1 year
–  12 Full Moons (months) in 1 year
–  Earliest year defined by Babylonians =360 days
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12 hours in day, 12 hours in night—Why?
–  Ancient Egyptian sundials
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10 + 2 Twilight hours
–  Night sky divided by 12 observable stars
–  Zodiac system
•  60 min/hour: Babylonian sexagesimal astronomy
–  Possibly because LCD divisible by 1-6, 10, 12, 15, 20, and 30
•  60 sec/min: Obvious choice once dial divided into 60
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Earliest Clocks
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3500BC: Egyptian Obelisk
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Structure which cast a shadow on the ground
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1500BC: Egyptian Sundial
1500BC: Egyptian Pharaoh Amenhotep buried with vessel-based water
clock (night clock)
1550BC to 500BC: Day/night first divided by passing of stars
500 to 300BC: Greek and Roman Mechanized water clocks
300BC to 200AD: Notion of a minute emerged
200AD: Far Eastern astronomical clocks
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1300AD: Primitive mechanical clocks begin to emerge (non water clocks)
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Mechanical Clocks
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1582: Galileo studies the characteristics of the pendulum
1656: Christiaan Huygens (Dutch) develops first mechanical clock based on
pendulum
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Achieved 10 seconds per day
1721: George Graham develops Dead Beat escapement and temperature
compensated pendulum
1761: John Harrison develops the ship s chronometer based on lever
escapement and balance wheel
1889: Siegmund Riefler develops first astronomical regulator (10ms per day
accuracy)
1889 and forward: Chester Henry Pond pioneers one of the most successful
synchronized time systems in history
Source: http://www.nist.gov/pml/general/time/index.cfm
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The Astronomical Regulator
•  Temperature compensated
Pendulums
•  Finest movements, ultra-accurate
•  Dead Beat Escapements
•  Sometimes encased in vacuum
•  Output electrical signals used to
synchronize other clocks
•  Accuracy in milliseconds per day
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The US Naval Observatory
What better place for an Astronomical Regulator?
•  1830: Started out as the US Depot of Charts and Instruments, for
regulation and repair of navigational chronometers and charts
•  1845: Time ball installed for Washington and Potomac area use
•  1854: Secretary of Navy declares this depot as the US Naval
Observatory and Hydrographic Office
–  Timekeeping declared as one of its most critical functions
–  Has served as a reference for Standard Time since 1865
•  Today: Synchronized to NIST by better than 100ns at any time
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How did Naval Observatory tell time?
•  Sidereal Time deduced from position of earth relative to stars
•  Solar Time deduced from position of sun relative to earth
•  Star (or sun) positions vs. fixed earth reference
–  eg, noon to noon passage of sun through meridian
•  Time transferred to Astronomical Regulators
•  Falling Time Ball at noon for local customers
–  Washington businesses and Departing ships
•  Coordinated time signal transmitted on Western Union telegraph
lines for 100 years from 1865
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Fun (and confusing) Time Facts Summary
•  Sidereal Day = 86,164.09053 seconds
•  Mean Solar Day ~ 87,600.002 seconds
•  UTC Day is 87,600 seconds
–  Based on the Atomic Second from TAI
–  Leap Second takes care of the difference
•  Atomic Second = 9,192,631,770 transitions of
a Cesium atom
–  Defines the second
–  Basis of the UTC (Coordinated Universal Time)
Source: Wikipedia
Confused yet? Let s simplify things!
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Coordinated Universal Time (UTC)
•  UTC is Coordinated Universal Time today
–  Primary standard for world timekeeping
–  Divides Time into Days, Hours, Minutes, Seconds
–  Successor of Greenwich Mean Time
•  UTC still referenced to Greenwich, England
–  Became official standard in 1961
•  Leap second concept introduced in 1972
–  Available via satellites, Network Time Protocol, WWV and WWVB
–  Referenced to TAI (International Atomic Time standard) offset corrected
with the Leap Second
•  Uses
–  Cell phones, online services, WWVB, GPS
–  Air traffic control, weather, synchronized time systems
–  Pretty much everything
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The Leap Second
One small step for a clock; one giant leap for mankind1
•  One second added periodically to the Day set by TAI
(International Atomic Time)
•  Compensates for variations in earth s rotation due to
tidal activity and other geophysical phenomena
•  Corrections made periodically
–  Difficult to predict for sure since it is irregular
–  Usually announced 8 weeks in advance of correction
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In 50 years up through 2011, 35 leap seconds
Last one added in 12-31-2008
Seem to be fewer lately
Next one predicted to be June 2012
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1Tom
van Baak
www.leapsecond.com
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Variability in Earth s Rotation
Source: http://tycho.usno.navy.mil/systime.html
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WWV and WWVB
•  NIST Radio Station in Fort Collins, Colorado at up to 10,000 Watts
–  Double sideband AM
•  Broadcasts 24 Hours per day, 7 days per week
•  Operates at 5 frequencies from 2.5MHz-20MHz
–  Separate transmitter and antenna for each frequency
•  UTC time (Greenwich referenced) in both voice and coded form
–  Must correct from Greenwich to local time zone
•  Weather and geophysical updates, alerts also available
•  WWVB since 1956
–  60KHz
–  Much more accurate
Source: http://www.nist.gov/pml/div688/grp40/wwv.cfm
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WWVB and Atomic Clocks
•  So-called commercial Atomic Clocks and
Atomic Watches are not at all atomic
–  They are radio-controlled
–  Broadcast from: WWVB in Fort Collins, CO
–  Broadcasting at 60KHz, 1 bit per second
•  WWVB uses UTC as a reference
))))))))
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The TAI reference
(Tempus Atomique Internationale)
•  Independent Atomic Clocks
•  Average of about 70 laboratories
–  200 Atomic clocks in all
•  This sets the length of one second
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The First REAL Atomic Clock
•  Constructed in 1949 by NBS (now NIST)
•  Accuracy 50 ppb (1.5 seconds per year)
using µ-wave spectroscopy of ammonia
–  Not much better than the earth s rotation
NBS Director Dr. Edward Condon and Dr. Harold Lyons with first Atomic clock
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Early Cesium Clocks
•  The 1955 NPL (UK) Cesium clock with accuracy of 1
second in 300 years
•  First commercial Cesium beam tube built by R. Daly of
National Company and J. Holloway of Varian Associates
(1967). Went on to be most widely used
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Fun Facts about Cesium
•  Discovered in 1860 by Robert Bunsen and Gustav
Kirchoff
•  Alkali metal, Atomic Number 55
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One electron in its outer atomic shell
Melting Point 28C (liquid at near room temps)
Similar to Rubidium and Potassium
VERY reactive with water
•  Cesium 133 is most stable isotope, used in clocks
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Modern Cesium (Atomic) Clock
•  Defines the Second
–  Duration of 9,192,631,770 cycles of radiation corresponding to
the transition between two hyperfine levels of the ground state of
cesium 133
•  Atomic time scale is the statistical second based on a
number of atomic clocks (eg, Naval Observatory Labs
has 70 of them)
•  Accuracy 2ns per day (2 parts in 1014 ) or 1 sec in
1,400,000 years (45 sec off since dinosaur extinction!)
HP/Agilent 5071A
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The HP/Agilent 5071A
•  So easy to use, your child could set it up!
Source: www.leapsecond.com
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The Atomic Wristwatch
Source: www.leapsecond.com
Bill checks the time on his atomic wristwatch
Backpack version
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Synchronized Time from 1884-1966:
The Self Winding Clock Company
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What was the need?
•  Transportation Revolution
–  Railroad, Cable Cars 1890s
•  Industrial Revolution
–  Need coordinated time
•  Communications widespread
–  Telegraph
–  Telephone
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Battery Technology ca. 1866-1896
Leclanche cell ca. 1866
• Used for doorbells, clocks prior to No. 6
• Patented; over 20,000 built
• Wet electrolyte: very sloppy
Columbia No. 6 Dry Battery ca. 1896
• National Carbon Co. of Lakewood, OH
• Founded 1894
• EM Jewett and George Little
• Solid electrolyte—Major breakthrough!
• Powered telephone, doorbells,
automobiles (ignitor), self-winding
clocks, lanterns, etc.
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Self Winding Clock Co. Wet Cell
$180 on Ebay
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Chester Henry Pond
•  Personal friend of Thomas Edison
–  Witnessed operation of first light bulb
•  Prolific Inventor; interested in telegraphs, clocks,
application of electromagnets and electricity
•  Founded the Self Winding Clock Co.
•  Pond (and other engineers at SWCC) developed:
–  Solenoid-based adjuster for synchronizing clocks
–  Winding Motor for early battery operated clocks
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Chester H. Pond Patents
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The Self Winding Clock Company
•  Primary business was manufacture and leasing of self winding clocks
–  Used in businesses, schools, transportation, financial institutions, etc.
•  Appear to have adapted movements manufactured by Seth Thomas
–  Probably licensed to ST
–  May have bought ST out of equipment to make parts later in history (not
clear)
•  Movements were very high quality with synchronization capability built
in (optional)
•  About 600 SWCC clocks migrated to the London Underground
–  American Engineers brought in by Charles Tyson Yerkes specified SWCC
–  Purchased from 1905-1929
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Example SWCC Movements
Rotary Motor: 1880s to early 1900s
Style A
Style B
Style C
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The Rotary Motor
Brushes (3)
Commutator
Electromagnets
(3)
Rotor
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Example SWCC Movements
The Style F Vibrating Motor: 1892 to 1960s
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The Vibrating Motor
Banking Springs
(2)
Contacts
(redundant)
Armature
Electromagnet
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SWCC Chime Clock
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Western Union
•  1830: Joseph Henry transmitted first signal over 1 mile of wire
•  1838: Samuel Morse demonstrated practical communication
system
•  1843: Congress funded 40 mile wire, Washington to Baltimore
•  1851: Western Union formed
–  New York and Mississippi Valley Printing Telegraph Company
–  Dispatching trains via telegraph
–  Changed name to Western Union in 1856
•  1861: First US transcontinental telegraph lines
–  Mainly along railroad rights of way
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1889-1963: Joined forces with Self Winding Clock Company
1914: First commercial charge card introduced
1933: First Singing Telegram
1974: First commercial satellite introduced by WU
Today: Primary business money transfers
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SWCC and Western Union
1889-1963
•  Entered into agreement in 1889
–  Transmission of time signals and maintenance of clocks
–  Cost to customer was $1.25-2.00 per month
•  1940: 100,000 subscribers to the service
–  Most subscribers had multiple clocks including both masters and slaves
–  Fell off after that as other methods of time synchronization emerged
Western Union
Master Clock
Slave Clocks
Naval Observatory
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Synchronized Time for the Masses
•  Unfortunately the SWCC + WU solution
was simply too expensive for the masses
•  Henry Warren realized that a more
commercially viable method was needed
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Worldwide Line Frequencies
•  Early AC frequencies were anywhere from 16.666Hz to
133Hz
–  25Hz at Niagra Falls—not good for lighting
•  Parts of Canada continued 25Hz until 1948
–  London in 1918 had 10 different frequencies
–  Some cities in Germany, Switzerland, Italy and other locations
were 40Hz, before standardizing to 50Hz from 1915-1946
–  Much of California used 50Hz until 1948
–  Western Japan 60Hz, Eastern Japan 50Hz
•  Still the case today!
•  USA established 60Hz as the standard in the 1920s but
there were exceptions
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Henry Warren
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Born in 1872, lived in Newton Centre, Mass
Enjoyed working with tools from an early age
MIT BSEE Graduate in 1894
Moved to Ashland, Mass in 1904
–  This is where Henry Warren developed 135 patentable inventions
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Developed the AC synchronous motor used in all electric clocks
Developed his Master Clock for regulating line frequency in 1916
GE bought half interest in the synchronous motor in 1917
Henry Warren decided on the trade name Telechron for his
products in 1923
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Telechron is Greek for Time from a Distance
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Patent 1,283,435
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Warren Telechron Clock Motors
Source: www.billsclockworks.com
Type B Motor Patents
Type A Motor
Type B Motor Capsule
A Look Inside B Rotor
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Warren Telechron Clock Motors 2
Source: www.billsclockworks.com
F Rotor
H Rotor
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Synchronous Motor—Theory
Analyzing Henry Warren s Patent
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Rotating magnetic field
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Shading 2 of the 4 poles
Rotor with ability to be magnetized
–  Called Remanence (hysteresis)
–  Dimensions, shape fairly critical
–  Warren used hard steel
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Big gap between rotor and poles
–  Prevent stray lines of force from
breaking synchronism
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Warren Type A Master Clock
By 1947 Warren masters regulated 95% of the power grid in the USA
Type A Master Clock
Type A Movement
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Type B Master Clock
Less accurate than Type A
•  Very clever design
•  Very attractive clock
•  Small dial indicates time from pendulum
movement
•  Movement uses differential gearing
•  Large indicator is difference between
pendulum clock and motor-driven clock
•  Error indicates how much generator
should be sped up or slowed down
•  Do not run clock with pendulum
stopped and clock plugged in
–  Will snap mainspring
Type B Master
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Interesting Telechron Clocks
Source: www.telechron.net/main.
Telechron Range Timer
Model 3T14 HMI
Telechron 355 Cathedral (pre-1930)
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More Interesting Telechron Clocks
455 The Radio (pre-1930)
661 The Concord (pre-1930)
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Other Electric Clock Manufacturers
Hammond
Hammond Polo
Skyscraper
Gregory
Postal Telegraph Wall
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How stable is AC line frequency in USA today?
Bottom Line: It always averages out to near perfect.
From www.leapsecond.com
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How accurate will AC line frequency in
USA be in the future?
•  Proposed change: Discontinue time error
corrections (TEC)
•  NAESB and NERC activity
–  Some proposals to tighten regulation 2000-2005
–  Superseded by others to eliminate it entirely 2005+
•  Three networks: Eastern, Western, ERCOT
–  Anecdotal indication that Eastern will be affected first, ERCOT
last if at all
But when will it occur?
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The Case to Eliminate TEC
From 2005 NERC study WEQBPS–004-000
1.  There is no clear reliability reason to perform Time
Error Correction.
2.  Discontinuing Time Error Correction would reduce
costs including maintenance of software, training
and implementation of the TEC procedures.
3.  The elimination of the present Time Error Correction
procedure would improve reliability as measured by
the variability of interconnection frequency.
4.  Based on study data from July 2005 Time Error
Correction was responsible for about half of the
frequency control failures (absolute line frequency
falling out of spec)
The only reason cited to maintain it is
for clocks!
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