Handbook 44 – 2009 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) 

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 

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5.55. Timing Devices Handbook 44 – 2009 

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 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. 

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Handbook 44 – 2009 5.55. Timing Devices 

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. 

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 

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5.55. Timing Devices Handbook 44 – 2009 

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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