TS 2139 HD 245.3 S2

TS 2139 HD 245.3 S2 is a standard for letter symbols used in electrical technology, focused on logarithmic quantities and the way their units are denoted. Its purpose is to support consistent technical notation in contexts where levels, ratios, gains, attenuation and similar quantities are expressed logarithmically, so that the same concept is not written in conflicting forms across engineering documents.

How logarithmic quantities are used in technical practice

Logarithmic expressions describe how much a quantity changes relative to a reference, rather than stating an absolute physical amount. In electrical and electronic work, this is especially useful for comparing power levels, signal levels, gain and loss. The distinction between the symbol for the quantity and the unit designation matters, because a logarithmic statement usually represents a level defined against a chosen reference, not a direct physical quantity in isolation.

What this standard covers

• Letter symbols used in electrical technology for logarithmic quantities and units
• Consistent notation for logarithmic quantities in technical writing
• Common technical presentation in engineering drawings, calculation sheets and documentation

The scope is concise and does not define equipment, test procedures or numerical performance limits. Instead, it supports a shared technical language for naming and presenting logarithmic quantities and units. That makes documentation easier to read, compare and exchange, especially in multilingual engineering environments.