Instructions for testing telegraph lines and the technical arrangements of offices
A technical manual by Louis Schwendler, published in London by Trübner in 1878, instructing telegraph engineers and office staff in testing lines and arranging equipment. Line engravings show wiring diagrams, Wheatstone bridge circuits, resistance coils with labelled values, keys and relays drawn as ringed discs, and a cutaway of an ink-recording instrument with its traced waveform.
