CALL MINING TELEPHONE
Comprising powerful five-magnet generator, 1,000 ohm detached call with 6 inch gongs, two inset receivers with rubber protecting caps, inset granular carbon microphone, induction 2 G.E.C. dry cells.
The whole is mounted in a water proof cast iron case, provided with and inner doors. The outer is secured by means of a substantial locking handle which is quickly and easily operated. This gives access. to the operative parts of the telephone. The inner door gives access to the interior when it is required to renew the microphone batteries.
It will be observed that the receivers are mounted on flexible arms. Raising either both of these to the ear brings the transmitter into the speaking position, and by means
working in long packed bearings operates the automatic switch contacts inside. This movement taking place every time the telephone is used maintains the microphone in a lively condition.
Elaborate precautions have been taken to meet the requirements of the Mines Department with regard to flameproof apparatus in fiery mines and at the same time to guard telephone from damage due to handling by mischievous and careless persons. The microphone and receivers are enclosed in metal cases which can only be opened by means a special key. In like manner a special key is required to open the inner door.
The generator contacts and automatic switch contacts are each enclosed in a flameproof a precaution which makes it possible to open the instrument with safety even a gaseous atmosphere.
It will be noticed that the whole of the working parts are mounted on the inner door which latter can be readily removed from its hinges and taken to the surface for repairs, if required, without the necessity of removing the entire telephone.
A bell is not fitted to the instrument but is supplied separately.
Cost in 1932 and 1935 was £19.10.0
Instrument only, without bell
Weight, 81 lbs.
Dimensions, l7.5 x 15.75 x 9.5 ins.
Taken from the 1932 and 1935 GEC catalogues
Last revised: February 01, 2011