Instructions for testing telegraph lines and the technical arrangements of offices
A technical manual by Louis Schwendler, electrician to the Indian government telegraph department, published in London by Trübner in 1878 for line testers and telegraph office staff. The plates are line diagrams of Wheatstone bridge circuits, galvanometers, battery stacks and branching lines, labelled with italic letters and arrows — usable as schematic ornament, arrow and coil motifs, or diagram frameworks.
