The Bell System technical journal
A corporate research periodical issued by American Telephone and Telegraph from 1922 onward for engineers and physicists working on telephony, transmission, and electrical measurement. The plates run to labelled line diagrams of laboratory apparatus in section \u2014 lenses, filters, rotators and hand wheels drawn in flat outline with leader lines and small-caps captions \u2014 useful for technical schematic styling, instrument silhouettes, and annotation conventions.
