Telephone Set F Mk I

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Telephone Set F Mk I
Signal Training Volume III, Pamphlet No. 23, Telephone Sets F Mk I, 1939 - Plate 1.jpg
Specifications
Weight 17 lb 4 oz
Length 12"
Width 7"
Height 8"

The Telephone Set F Mk I is a portable instrument for army communication. It is not normally used forward of divisional headquarters.[1] It provides the follow facilities:

Calls by buzzer
Calls by magneto generator
Responds by bell to magneto generator calling
Responds by aural indication to buzzer calling
Speech communication

The telephone is 12” long by 7” wide by 8” deep weighing 17 lbs. 4 oz. and is housed in a hinged wooden box for carrying and storage. The set can be removed from its case by depressing a metal spring tab, or alternatively, the spring tab has a second stop leaving the set somewhat inside the case where it can be operated protected from inclement weather. The set has a cast alloy body with provision for the handset socket and cradle, a buzzer, ringers, line connections and a magneto generator operated by a crank. Power is supplied by two 1.5 volt “X” or “S” cells in a wax lined battery compartment on the left side of the set. The magneto and gears are in the centre and the buzzer slides in vertically on the right. Access to the batteries, magneto and buzzer is by way of removable caps on the top of the set. There is no provision for a Morse key as there was in other telephone sets designed for use in more forward areas.[2]

Reliable voice range was 13 to 18 miles with twisted D8 wire, however range would be reduced with wet wires, poor connections or wires run along the ground. Two wires (Line 1 and Line 2) could be used, or alternatively, Line 2 could be grounded with an earthing spike and only a single Line 1 wire used between sets. Under good conditions this could actually increase the working range.

The Telephone Set F Mk I* is similar to the Telephone Set F Mk I except for a small constructional difference.

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References

  1. Signal Training Volume III. Pamphlet No. 23. Telephone Sets, F, Marks I and I*. 1939.
  2. With information from Bruce Parker.