Operation and adjustments of the automatic three wire telephone
A 1915 engineering thesis by Benjamin Harrison Decker, submitted at the University of Illinois, explaining the operation and adjustment of the automatic three-wire telephone for instructors and telephone engineers. The plates are thin-line pencil or pen tracings of switch-hook mechanisms, coil springs, contact levers and slotted screws, keyed with small numerals, printed light enough that the letterpress text shows through from behind.
