CONTENTS

 1     Introduction
 2     References
 3     Fundamentals about dB
        3.1     Loss and gain
        3.2     The letter "p" in "dBmp" and "dBm0p"
        3.3     Correction factors
                  3.3.1     Sending a test signal
                  3.3.2     Receiving a test signal
        3.4     Signal-to-noise ratio
        3.5     Sound pressure level
 4     The use of a reference signal
 5     Relations between the units "dBm","dBr" and "dBm0"
        5.1     General
        5.2     The unit "dB"
        5.3     The unit "dBm"
        5.4     The unit "dBr"
        5.5     The unit "dBm0"
        5.6     The relationship between dBm, dBr and dBm0
        5.7     The unit "dBov"
        5.8     Relation between overload (dBov) and maximum levels (dBm0)
 6     The concept of "relative levels"
        6.1     General principles
        6.2     Circuits and connections
        6.3     The speech signal and the dynamic range of the voice channel
        6.4     Relative level designations for a digital path
        6.5     Relative levels in equipment design, specification and testing
                  6.5.1     Analogue equipment
                  6.5.2     Codecs and digital pads
                  6.5.3     Relative level of a point in a digital link
                  6.5.4     Digital exchanges
        6.6     Relative levels in transmission planning and maintenance
Appendix I – The neper
        I.1        Introduction
        I.2        Definition of the neper
        I.3        Use of the decibel and of the Neper