Types AB 2530-2535
Magneto Wall Telephones for Mines
FRAMEWORK, cast iron, enamelled.
MICRO-TELEPHONE. RE 9210, with enclosed terminals, suspended vertically on a hook-switch, complete with waterproof cord RS 6100 (Old No. 2495), which is protected by a flexible metal tube. The transmitter is of the interchangeable inset type, with a patent mouthpiece.
These telephones are divided into two portions, and the outer door, when closed, makes the case perfectly watertight.
When the outer door of the case is unlatched and opened, the micro-telephone clamped on the switch-hook with its flexible cord and the generator crank are all that are exposed to view.
The inner portion of the case which is made watertight by the door on which the micro-telephone is clamped, contains:-
GENERATOR. For type and number of magnets see table below. AB 2535 is shown right.
These generators ring satisfactorily through a line resistance of 25,000 ohms.
RINGER. For resistance see table below. The gongs are fitted outside the case, so as not to deaden the sound, but are protected.
BATTERIES. Two dry cells, RK 190 (Old No. 600).
TERMINALS. For the line, extension bell, and earth, etc.
It is not necessary to open the inner door when using the telephone.
Incoming wires are brought to the terminals through two holes on the top side of the telephone, these holes being so formed that they may be hermetically closed by filling in with some suitable paste or compound, after the wires have been led in.
These holes are also threaded at the top, thus permitting iron or other tubes to be screwed on, to protect the wires, if desired.
In consequence of these special arrangements these telephones are very suitable for use in mines and other places where they are exposed to damp, and rough usage.
|Type||Generator type||Generator magnets||Ringer resistance|
|AB 2530||RH 4110||4||300|
|AB 2535||RH 5201||5||2000|
Length 17.5 inches.
Weight 57.5 lbs.
Taken from the Ericsson Telephone Catalogue 1912
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