The Telephone Set D Mk V (often nicknamed the “Don Five”) was a portable field telephone used by Commonwealth armies during the Second World War. It provided reliable, low-tech communication over telephone cable laid on the ground, connecting headquarters, company positions, and other command posts—especially in areas where radio was unreliable, insecure, or unnecessary.

What it did

This set supported:

• Speech (normal voice conversation) over field cable

• Morse signalling using the set’s built-in key and buzzer

• Calling by buzzer, with different alerting methods depending on whether it was connected directly to another phone or through a switchboard/exchange

How it worked

Unlike a home phone, this was not connected to a public network. Signals troops (or anyone tasked with communications) would run wire between positions and plug the phone into that line.

A key point: the D Mk V could call out using a buzzer, but it did not generate its own magneto ringing current. Its internal bell could be rung by another instrument or switchboard that had a magneto generator. In practice, it worked well either phone-to-phone on a simple line, or as part of a larger switchboard system.

Range and performance

Actual performance depended on line quality, splices, moisture, and how the cable was laid, but published guidance gives these typical maximum ranges:

• Speech: up to 14–16 miles using D8 twisted cable, or 8–10 miles using D3 cable

• Morse: up to 25 miles (D8), or 15 miles (D3)

Canadian service and scale of issue

This pattern of field telephone appears in Canadian organizational equipment authorizations during the war. For example, a Canadian Motor Battalion line-equipment authorization (Nov 1940) includes 8 Telephone Sets, D, Mk V as part of its line communications equipment.

Manufacturing

These telephones were produced under wartime contract by multiple manufacturers. Canadian-marked examples are known from P.E.W. Ltd (commonly expanded in references as Phoenix Telephone and Electric Works).

Specifications (as typically listed for the set)

• Type: Portable field telephone

• Pattern/Model: Telephone Set D Mk V

• Date: 1940 (as noted for this example)

• Communications: Speech and Morse (by buzzer and key)

• Calling/alerting: Calls by buzzer; can respond via bell when rung by magneto-equipped instrument/exchange

• Power: Two 1.5V dry cells (commonly described as “X” or “S” cells in period references)

• Typical cable types referenced: D8 twisted cable, D3 cable

• Typical maximum range: 14–16 miles speech / 25 miles Morse (D8); 8–10 miles speech / 15 miles Morse (D3)