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telegraph units of electrical resistance

Prior to the introduction and standardization of the ohm, engineers building telegraph systems had an acute need for a unit of resistance, and they devised a number of short-lived, often local, units to meet that need.

A French unit, attributed to Digney: the resistance of 1 kilometer of iron wire 4 mm in diameter. About 9.266 B.A. ohms¹, about 9.142 true ohms. In 1867, redefined as 10 Siemen's units, about 9.534 ohms.
A unit attributed to Brèguet. About 9.760 B.A. ohms¹, about 9.629 true ohms.
A Swiss unit, following Hipp. About 10.42 B.A. ohms¹, about 10.28 true ohms. In 1867, redefined as 10 Siemen's units, about 9.534 ohms.
A German unit by 1848, 1 German Meile (7532.83 meters) of copper wire ¹⁄₁₂ of an inch (2.1 millimeters) in diameter at 20° centigrade. About 57.44 B.A. ohms¹, about 56.67 true ohms. Superceded by the Siemen's unit.
An American unit, the resistance of one statute mile of No. 9 iron wire. The American Telegraph Company had standards wound to support use of this unit. Superceded by the B. A. ohm.

In addition the Varley unit and the Mathiessen unit (both based on an English statute mile of wire) were telegraph units.

1. British Assn. for the Advancement of Science.
Reports of the Committee on Electrical Standards appointed by the British Assn. for the Advancement of Science...With a report to the Royal Society on units of electrical resistance, by Prof. F. Jenkin....
London: E. & F. Spon, 1873.

H. Schoentjes.
Les Grandeurs Électriques et leurs Unités. 2nd ed. revised and augmented.
Paris: Librairie de Gauthier-Villars Éditeur, 1884.

Page 102.

Ernest Spon, editor.
Supplement to Spons' Dictionary of Engineering, Civil, Mechanical, Military, and Naval. Division II.
London: E. & F. N. Spon, 1880.

Page 550.