GEC
TEL/1I/MWU

Intrinsically safe magneto telephone
This instrument is intended for use underground in a coal mine, but is equally suitable in other situations where rough usage is anticipated, provided no dangerous atmosphere (other than methane) exists.

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.

Certification
Certificate of intrinsic safety for methane, No. T/TEL 17, certified by the Ministry of Power.

Dimensions
Dimensions in brackets are the equivalent in cm.
Height - 19.25 inches (48.89cm) 
Width - 14.25 inches (36.19cm)
Depth - 10.75 inches (27.30cm)

Weight
80lb (36.3kg)

Renumbered in 1955 was originally the K8100

Last revised: January 27, 2011