BELL TELEPHONE MANUFACTURING Co.
(BTMC) ANTWERP
Telephone No. 2871

Explosion-Proof Telephone

The Telephone No. 2871 was developed for use in gassy mines. It is a centrally located switch that can be used in both automatic and manual networks. It is intended to be connected to the surface networks serving the coal mine, but as approved by both the Belgian Mining Authority and the Belgian Telegraph and Telephone Authority, the No. 2871 can also be used to communicate, via the surface switch, with subscribers of the public networks. Thus, thanks to this type of device, underground personnel can remain constantly in contact with the outside world, which offers considerable advantages from an operational safety standpoint.

The Telephone No. 2871 is made of cast iron and is circular in shape; it consists of two interlocking parts. To prevent accidental opening of the unit, the two parts of the casing are assembled using triangular-headed screws, one of which is further protected by a flap controlling a safety device.

The microphone is housed within the casing itself.  The telephone includes two separate earphones; each is housed in a metal handle fitted with a fixed horn that is screwed in place. These earphones are suspended from a hook on each side of the casing.

The openings are lined with fine copper wire, thus separating the inside of the unit from ambient noise. The cable and cord entries are lined with safety plugs.

The line wires are connected to a block designed so that the exposed wires and contact springs cannot be touched, even accidentally.

All components are treated to resist corrosion, especially humidity, prevalent in tropical countries.

The No. 2871 telephones are complete units and require no additional accessories or equipment.

The No. 2871A and No. 2871C are for use on automatic networks and are equipped with a transfer button, while the No. 2871B and No. 2871D are for use on manual networks and do not have a transfer button.

Dimensions
Width: 214mm (340 mm overall).
Height: approximately 340mm (overall).
Depth: 125mm.

Weight: 8kg.

Taken from the BTMC Catalogue - 1952