MAGNETO WALL PATTERN
Intrinsically safe magneto telephone
The instrument case is a very strong iron casting, the front hinged and secured to the body by hexagon head bolts for which a spanner is provided. A chamber is fitted to the base containing line and extension bell terminals, with two screwed entries to take cable glands. The generator, which has “Alnico” magnets, is coupled to a substantial handle via a canvas drive and watertight gland. The 1000 ohm polarised ringer operates a 6 inch gong.
The inset transmitter is fitted in an iron chamber on the front, protected by metal gauze. An inset receiver inside the case operates via a flexible metallic tube to an acoustic earpiece. When the listening tube is lifted to the ear it actuates (via a watertight gland in the case) a cam which operates the switch springs controlling the speaking battery and receiver circuits. Two BA 4935 G.E.C. dry cells are mounted in metal containers on the inside of the door. A suitable extension bell is the K 8312 type.
Last revised: January 27, 2011