Handbook 44 – 2010 5.55. Timing Devices 

Table of Contents 

Section 5.55. Timing Devices................................................................................................. 5-35

A. Application .................................................................................................................................................. 5-35

S. Specifications............................................................................................................................................... 5-35

S.1. Design of Indicating and Recording Elements and of Recorded Representations............................. 5-35

S.1.1. Primary Elements................................................................................................................. 5-35

S.1.2. Graduations.......................................................................................................................... 5-36

S.1.3. Indicators. ............................................................................................................................ 5-36

S.1.4. Printed Tickets. .................................................................................................................... 5-36

S.2. Marking Requirements, Operating Instructions................................................................................. 5-36

N. Notes............................................................................................................................................................. 5-36

N.1. Test Method. ...................................................................................................................................... 5-36

N.2. Broadcast Times and Frequencies...................................................................................................... 5-37

T. Tolerances.................................................................................................................................................... 5-37

T.1. Tolerance Values. .............................................................................................................................. 5-37

T.1.1. For Timing Devices Other Than Those Specified in T.1.2. For Time Clocks and Time 

Recorders and T.1.3. On Parking Meters............................................................................. 5-37

T.1.2. For Time Clocks and Time Recorders. ................................................................................ 5-37

T.1.3. On Parking Meters. .............................................................................................................. 5-37

T.2. Tests Involving Digital Indications or Representations. .................................................................... 5-38

UR. User Requirements ..................................................................................................................................... 5-38

UR.1. Statement of Rates. ............................................................................................................................ 5-38

UR.2. Time Representations......................................................................................................................... 5-38

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Handbook 44 – 2010 5.55. Timing Devices 

Section 5.55. Timing Devices 

A. Application 

A.1. This code applies to devices used to measure time during which services are being dispensed (such as vehicle 

parking, laundry drying, and car washing). 

A.2. See also Section 1.10. General Code requirements. 

S. Specifications 

S.1. Design of Indicating and Recording Elements and of Recorded Representations. 

S.1.1. Primary Elements. 

S.1.1.1. General. – A timing device shall be equipped with a primary indicating element, and may also 

be equipped with a primary recording element. A readily observable in-service light or other equally 

effective means that automatically indicates when laundry driers, vacuum cleaners, and car washes are in 

operation shall be deemed an appropriate primary indicating element. 

(Amended 1979) 

S.1.1.2. Units. – A timing device shall indicate and record, if the device is equipped to record, the time 

in terms of minutes for time intervals of 60 minutes or less and in hours and minutes for time intervals 

greater than 60 minutes. 

S.1.1.3. Value of Smallest Unit. – The value of the smallest unit of indicated time and recorded time, if 

the device is equipped to record, shall not exceed the equivalent of: 

(a) one-half hour on parking meters indicating time in excess of 2 hours; 

(b) six minutes on parking meters indicating time in excess of one but not greater than 2 hours; or 

(c) five minutes on all other devices, except those equipped with an in-service light. 

(Amended 1975) 

S.1.1.4. Advancement of Indicating and Recording Elements. – Primary indicating and recording 

elements shall be susceptible to advancement only during the mechanical operation of the device, except 

that clocks may be equipped to manually reset the time. 

S.1.1.5. Operation of In-Service Indicator Light. – The in-service light indicator shall be operative 

only during the time the device is in operation. 

S.1.1.6. Discontinuous Indicating Parking Meters. – An indication of the time purchased shall be 

provided at the time the meter is activated in units of no more than 1 minute for times less than 1 hour and 

not more than 2 minutes for times of 1 hour or more. Convenient means shall be provided to indicate to the 

purchaser the unexpired time. 

(Added 1975) (Amended 1976) 

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5.55. Timing Devices Handbook 44 – 2010 

S.1.2. Graduations. 

S.1.2.1. Length. – Graduations shall be so varied in length that they may be conveniently read. 

S.1.2.2. Width. – In any series of graduations, the width of a graduation shall in no case be greater than 

the width of the minimum clear interval between graduations and the width of main graduations shall be 

not more than 50 % greater than the width of subordinate graduations. Graduations shall in no case be less 

than 0.2 mm (0.008 in) in width. 

S.1.2.3. Clear Interval Between Graduations. – The clear interval shall be not less than 0.75 mm 

(0.03 in). If the graduations are not parallel, the measurement shall be made: 

(a) along the line of relative movement between the graduations at the end of the indicator, or 

(b) if the indicator is continuous, at the point of widest separation of the graduations. 

S.1.3. Indicators. 

S.1.3.1. Symmetry. – The index of an indicator shall be symmetrical with respect to the graduations, at 

least throughout that portion of its length associated with the graduations. 

S.1.3.2. Length. – The index of an indicator shall reach to the finest graduations with which it is used, 

unless the indicator and the graduations are in the same plane, in which case the distance between the end 

of the indicator and the ends of the graduations, measured along the line of the graduations, shall be not 

more than 1.0 mm (0.04 in). 

S.1.3.3. Width. – The width of the index of an indicator in relation to the series of graduations with 

which it is used shall be not greater than: 

(a) the width of the widest graduation, and 

(b) the width of the minimum clear interval between the graduations. 

S.1.3.4. Parallax. – Parallax effect shall be reduced to a practicable minimum. 

S.1.4. Printed Tickets. – A printed ticket issued or stamped by a timing device shall have printed clearly 

thereon: 

(a) the time and day when the service ends and the time and day when the service begins, except that a 

self-service money-operated device that clearly displays the time of day need not record the time and 

day when the service begins; or 

(b) the time interval purchased, and the time and day that the service either begins or ends. 

(Amended 1983) 

S.2. Marking Requirements, Operating Instructions. – Operating instructions shall be clearly stated on the 

device. 

N. Notes 

N.1. Test Method. – A timing device shall be tested with a timepiece with an error of not greater than plus or 

minus 15 seconds per 24-hour period. In the test of timing devices with a nominal capacity of 1 hour or less, 

stopwatches with a minimum division of not greater than one-fifth second shall be used. In the test of timing 

devices with a nominal capacity of more than 1 hour, the value of the minimum division on the timepiece shall be 

not greater than 1 second. Time pieces and stopwatches shall be calibrated with standard time signals as described 

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Handbook 44 – 2010 5.55. Timing Devices 

in National Institute of Standards and Technology Special Publication 432, NIST Time and Frequency 

Dissemination Services, or any superseding publication. 

(Amended 1978) 

N.2. Broadcast Times and Frequencies. – Time and frequency standards are broadcast by the stations listed in 

Table N.2. Broadcast Times and Frequencies. 

Table N.2.* 

Broadcast Times and Frequencies 

Station 

Location, 

Latitude, 

Longitude 

Frequency 

(MHz) 

Times of 

Transmission 

(UTC) 

WWV 

Fort Collins, Colorado 

40Ε41' N 

105Ε02' W 

2.5 

5.0 

10.0 

15.0 

20.0 

Continuous 

WWVH 

Kauai, Hawaii 

21Ε59' N 

159Ε46' W 

2.5 

5.0 

10.0 

15.0 

Continuous 

CHU 

Ottawa, Canada 

45Ε18' N 

75Ε45' W 

3.330 

7.335 

14.670 

14.670 

Continuous 

*From NIST Special Publication 559, “Time and Frequency Users’ Manual,” 1990. 

(Added 1988) 

T. Tolerances 

T.1. Tolerance Values. – Maintenance and acceptance tolerances for timing devices shall be as follows: 

T.1.1. For Timing Devices Other Than Those Specified in T.1.2. For Time Clocks and Time Recorders 

and T.1.3. On Parking Meters. – The maintenance and acceptance tolerances shall be: 

(a) On Overregistration: 5 seconds for any time interval of 1 minute or more; and 

(Amended 1986) 

(b) On Underregistration: 6 seconds per indicated minute. 

(Amended 1975) 

T.1.2. For Time Clocks and Time Recorders. – The maintenance and acceptance tolerances on overregistration and underregistration shall be 3 seconds per hour, but not to exceed 1 minute per day. 

(Amended 1975) 

T.1.3. On Parking Meters. – The maintenance and acceptance tolerances are shown in 

Table T.1.3. Maintenance and Acceptance Tolerances for Parking Meters. 

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5.55. Timing Devices Handbook 44 – 2010 

Table T.1.3. 

Maintenance and Acceptance Tolerances for Parking Meters

Maintenance and Acceptance Tolerances 

Nominal time capacity On overregistration On underregistration 

30 minutes or less No tolerance 10 seconds per minute, 

but not less than 2 minutes 

Over 30 minutes to and 

including 1 hour No tolerance 5 minutes plus 4 seconds 

per minute over 30 minutes 

Over 1 hour No tolerance 7 minutes plus 2 minutes 

per hour over 1 hour 

T.2. Tests Involving Digital Indications or Representations. – To the tolerances that would otherwise be 

applied, there shall be added an amount equal to one-half the minimum value that can be indicated or recorded. 

UR. User Requirements 

UR.1. Statement of Rates. – The price in terms of money per unit or units of time for the service dispensed and 

the number of coins the device will accept and be activated by at one time, shall be clearly, prominently, and 

conspicuously displayed. 

(Amended 1976) 

UR.2. Time Representations. – Any time representation shall be within plus or minus 2 minutes of the correct 

time in effect in the area, except on an individual clock used only for “time out”; in addition, the time indication of 

the “time-out” clock shall be the same as or less than that of the “time-in” clock. 

(Amended 1975) 

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