2 BELL SYSTEM TECHNICAL JOURNAL 



this matter was discussed. In this joint consideration there arose the 

 suggestion that the fundamental unit on the decimal basis be defined 

 to be equal in magnitude to that of ten transmission units, so that the 

 basic power ratio would be 10^ The units proposed thus came to one 

 based on the power ratio of 10^ and the other on the power ratio of e~, 

 with the provision that decimal submultiples of either unit could be 

 employed, using the customary prefixes to give the proper indication. 

 On this basis, the numbers of the two kinds of units corresponding to a 

 given power ratio, differ by about 15 per cent. It was further sug- 

 gested that the naperian. unit be called the "neper" and that the 

 fundamental decimal unit be called the "bel," these names being 

 derived respectively from the names of Napier, the inventor of natural 

 logarithms, and Alexander Graham Bell. 



These joint considerations have had the following results. The 

 European International Advisory Committee has recommended to 

 the various European telephone administrations that they adopt 

 either the decimal or naperian unit and designate them the "bel" and 

 "neper" respectively. The Bell System has adopted the name 

 "decibel" for the "transmission unit," based on a power ratio of 10-^ 

 This is in accordance with the terminology for the decimal unit, the 

 prefix "deci" being the usual one for indicating a one-tenth relation. 

 For convenience, the symbol "db" will be employed to indicate the 

 name "decibel." 



* References: 



"The Transmission Unit and Telephone Transmission Reference Systems," 



W. H. Martin, A.I.E.E. Trans., Vol. 43, pp. 797-801, 1924, and B.S.T.J., 



Vol. 3, pp. 400-408, July, 1924. 

 "The Transmission Unit," R. V. L. Hartley, Electrical Communications, Vol. 3, 



pp. 34-42, June, 1924. 

 "Telephone Transmission Standards," Dr. F. Breisig, The Electrician, Vol. 94, 



pp. 114-115, Jan. 30, 1925. 

 "Telephone Transmission Units," Colonel T. F. Purves, The Electrician, Vol. 94, 



pp. 144-145, Feb. 6, 1925. 

 "Telephone Transmission," G. D. Hood, The Electrician, Vol. 94, p. 369, March 



27, 1925. 

 "Telephone Transmission Standards," Dr. F. Breisig, The Electrician, Vol. 94, 



pp. 454-455, April 17, 1925. 

 "The Telephone Transmission Unit," Colonel T. F. Purves, The Electrician, 



Vol. 94, pp. 535-542, May 8, 1925. 

 "Telephone Transmission Unit," F. B. Jewett, The Electrician, Vol. 94, pp. 



562-563, May 15, 1925. 

 " Telephone Transmission Units," Dr. F. Breisig, The Electrician, Vol. 94, p. 630, 



May 29, 1925. 

 "The Telephone Transmission Unit," Dr. F. Luschen, The Electrician, Vol. 95, 



pp. 94-95, July 24, 1925. 



