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Part 1 Definition of expressions used in the Schedule

Original text. Later amendments are not shown.

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.