# Unit conversion formula chart pdf

This article is about the unit of level. That is, a change in power unit conversion formula chart pdf a factor of 10 corresponds to a 10 dB change in level. When expressing field quantities, a change in amplitude by a factor of 10 corresponds to a 20 dB change in level. The extra factor of two is due to the logarithm of the quadratic relationship between power and amplitude.

The decibel scales differ so that direct comparisons can be made between related power and field quantities when they are expressed in decibels. The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. 1 TU was defined such that the number of TUs was ten times the base-10 logarithm of the ratio of measured power to a reference power level. 10 logarithm of the power ratio.

The bel is seldom used, as the decibel was the proposed working unit. Since the earliest days of the telephone, the need for a unit in which to measure the transmission efficiency of telephone facilities has been recognized. The introduction of cable in 1896 afforded a stable basis for a convenient unit and the “mile of standard” cable came into general use shortly thereafter. This unit was employed up to 1923 when a new unit was adopted as being more suitable for modern telephone work. The new transmission unit is widely used among the foreign telephone organizations and recently it was termed the “decibel” at the suggestion of the International Advisory Committee on Long Distance Telephony. The number of transmission units expressing the ratio of any two powers is therefore ten times the common logarithm of that ratio.