T.E.R. No.1
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[ Note ]
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 Front Left |
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 Back Left |
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 Slider Back Left |
 Slider Back Right |
 Inside Well, Center |
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This slide rule was designed to calculate "Telephone Equivalent Resistance
(T.E.R.)" for use by the General Post Office (then in charge of Telecommunication
as well as Postal service.) A pair of wires that originate from an exchange office and eventually reach a telephone set usually consist of wires of two sections of different wire diameters. Engineers had to make sure that any particular configuration (wire diameters and lengths) would give electrical resistance within the limit. The scales on this rule are linear, rather than logarithmic. |
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