INTRINSICALLY SAFE MAGNETO WALL PATTERN
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.
Certificate of intrinsic safety for methane, No. T/TEL 17, certified by the Ministry of Power.
Height - 19.25in. (48.89cm)
Width - 14.25in. (36.19cm)
Depth - 10.75in. (27.30cm)
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” 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.
See also K8100, which was the earlier
Catalogue number for this phone.