[GreenKeys] Polar and neutral loops and all that

[jhhaynes at earthlink.net]

A good reference for all kinds of wire-line technology, as well as basic
teleprinter theory, is the book "Principles of Electricity Applied to
Telephone and Telegraph Work", an AT&T Long Lines publication.
Fortunately these are widely available at quite reasonable prices.
See www.abebooks.com

There are three editions: 1938, 1953, and 1961.  The telegraphy 
information is pretty much the same in all of them.  There is also a 1941
printing said to be a reprinting with corrections of the 1938 edition.

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jhhaynes at earthlink dot net