GEC K8100

MAGNETO CALL
WATER-TIGHT TELEPHONE

K8100 (Closed)                                   K8100 (Open for inspection)

Consisting of a substantial Cast-iron Case, treated with a special rust and damp-proof varnish, and fitted with the following apparatus: Four magnet Generator, Polarized Call Bell, 'Solid Back' long distance speaking Granular Carbon Transmitter, Double-pole 'Bell' Receiver, Induction Coil, Lightning Protector and Fuses, Automatic Switch and Two Dry Cells. 

The whole of this apparatus, with the exception of the 'Bell' Receiver, is enclosed in an inner compartment with a door, which can be locked to prevent tampering with the interior fittings. The outer door is provided with a Rubber Seating, thereby effectually preventing the entrance of moisture to the apparatus. 

The Armature of the Generator, Bell Coils, Induction Coil, and Receiver Coils are specially insulated to resist moisture. The Line Wires are connected to Terminals, enclosed in a small protecting Cap at the bottom of the case.

Taken from the GEC Telephone Catalogue, K Section, 10th Edition, 1908

K8100

MAGNETO CALL MINING TELEPHONE
(CERTIFIED BY H.M. MINES DEPARTMENT)
FLAMEPROOF AND INTRINSICALLY SAFE

1916 model

1932 model

Text taken from the 1916 catalogue

Specially designed to meet mining requirements and to comply with H.M. Home Office Regulations. The cast-iron case is strong and well finished, particular care being taken to make the joint between the case and lid flameproof as well as watertight. Specially designed to meet mining requirements The flanges are one inch in width and machined so as to cool effectively any hot gases escaping as as the result of an internal explosion. The cover is securely bolted to the case. The internal unoccupied space is kept down to a minimum so as to limit the amount of explosive gas which might accumulate.

The equipment comprises:

Powerful Generator, with canvas drive, and fitted with strong handle working through a flameproof and watertight gland.

Polarised Ringing Movement wound to a resistance of 1,600 ohms and fitted with 6 inch gong. The bobbins are wound with enamelled wire.

Solid Back Long Distance Transmitter fitted in an iron chamber on the front of door, the diaphragm being protected from damage by a fine-meshed brass gauze. An induction coil wound with enamelled wire is fitted inside the case.

Double Pole Bell Receiver. This receiver is fitted inside the case and is arranged so as to revolve when the listening tube (which is fitted on the left-hand side) is lifted to the ear.. At the diaphragm end of the receiver a cam is fitted. This revolves with the receiver and at the same time operates the switch springs controlling the speaking battery and receiver circuits. The gland through which the tube passes is flameproof and watertight.

Two No. 2 G.E.C. Dry Cells are fitted in metal containers which are mounted on the inside of the door by means of a metal band.

Attached to the bottom of the case is a chamber which contains strong and well designed line terminals.

Four lugs are fitted on the sides and back of the instrument for fixing.

Weight. 80 lbs.

Dimensions. 19.25 x 14.25 x 10.75 ins

Cost in 1916 was £10.0.0
Cost in 1935 was £18.18.0

In 1955 this telephone was renumbered the TEL/1I/MWU

Last revised: January 27, 2011