"Bill Gill" wrote in message ...

The transmission unit (TU) was devised by engineers of the Bell
Telephone Laboratories in the 1920s to replace the MSC. 1 TU
was defined as ten times the base-10 logarithm of the ratio of
measured power to a reference power level.[5] The definitions
were conveniently chosen such that 1 TU approximately equaled
1 MSC (specifically, 1.056 TU = 1 MSC).

This is possible, but it sounds like retroactive justification.