TS 2139

TS 2139 is a standard for letter symbols used in electrical technology when dealing with logarithmic quantities and their units. In electrical and communications practice, logarithmic notation is used to express very wide ranges in a compact way, so the quantity, the unit, and the symbol need to be distinguished carefully rather than treated as interchangeable.

What logarithmic quantities mean in engineering use

Logarithmic quantities do not describe a direct measured magnitude on a linear scale; they express a level or ratio. This is especially common for transmission-related quantities, levels, frequency intervals, and quantities associated with information content. Using a logarithmic scale makes large and small values easier to compare within one framework and is widely practical in engineering calculation and communication.

Core concepts covered by the standard

• Logarithmic quantities such as transmission path quantities, levels, frequency interval, and information-content-related quantities.
• Units for logarithmic quantities, including the neper, bel, and octave.
• Letter symbols associated with these quantities, supporting consistent technical notation.
• The standard focuses on naming and expression rather than on interpreting the quantities or tying them to a specific application.

In general technical documentation, standards of this kind help keep calculations, measurements, catalog data, and reports consistent. Logarithmic expressions are common in electrical engineering, acoustics, and signal transmission, and the correct symbol helps indicate both the type of quantity and the scale being used.

This record was issued on the basis of IEC 27-3:1974 and later withdrawn. TS 2139 therefore represents a historical reference point for the notation and naming of logarithmic quantities in electrical technology.