NATIONAL TELEPHONE COMPANY
Mining and Engine House Telephones
Pattern No. B385
Comprises - An Enclosed Wood Wall Box saturated with oil, (and outwardly covered with Sheet Lead to prevent the corrosive action of the acid liquids
and vapours met with in Mines), Solid Back Transmitter, Fixed Receiver with Flexible
Tube, Induction Coil, two Dry Cells, a Knob-handle Switch and the separate large size
No automatic switch is provided, but an outside knob is arranged to be turned and held whilst speaking is going on.
Last revised: July 07, 2020