# The Wireless Telegraphy (Control of Interference from Radio-Frequency Heating Apparatus) Regulations 1971, Part 1: Definition of expressions used in the Schedule


Voltage and e.m.f.
References to the voltage or e.m.f. of a sinewave are references to its effective or root mean square value.
Decibel (abbreviated dB)
A unit of transmission giving the ratio of two powers.
If P1 and P2 represent two values of power, and n the number of decibels representing their ratio:
n = 10 ⁢ log10 ( P1 P2 )
If the two powers are dissipated in equal resistive impedances, their ratio in decibels may be expressed by:
n = 20 ⁢ log10 ( V1 V2 ) V1, V2 are the voltages across the two resistive impedances.
Terminal voltage calibration constant
The number of decibels that must be added to the reading of the measuring apparatus, when a measurement of terminal voltage is made as prescribed, to give the terminal voltage in decibels above 1 microvolt.
Field strength calibration constant
The number of decibels that must be added to the reading of the measuring apparatus, when a measurement of field-strength is made as prescribed, to give the value of field-strength in decibels above 1 microvolt per metre.

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Source: https://www.legislation.gov.uk/uksi/1971/1675/schedule/2/part/1 (the official version)
Page: https://openlegislation.uk/wireless-telegraphy-control-of-interference-from-radio-frequency-heating-apparatus-regulations-1971/schedule-2/part-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.