Eighty years ago, Britain was at war, but that didn’t stop students from building instructional instruments, as shown by these plans for a telephone appearing in the November 1944 issue of Practical Mechanics.

The set was based upon the original telephone of Alexander Graham Bell, and could be built by senior schoolboys in the science room using readily available material. The magazine provided all of the construction details. Two instruments could be used to communicate from one room to another, strictly with sound power. For longer distances, the magazine recommended a carbon microphone with a battery running to the phone.

It could also be used as an extension for a Morse buzzer. All construction could be done with a few simple hand tools. The most delicate part of the operation was spacing the diaphragm just the right distance from the permanent magnet.