WESTERN UNION SPECIAL EVENTS SET
Portable sets were in use throughout the era of the Morse telegraph. From the first box relay, to the "pocket relay", portable sets played an important role in the history of the telegraph.
One of the very last of the portable sets was used by Western Union to cover special events. This set is very unique in that it does not use a conventional sounder. Instead, a telephone headset is used to produce the clicking sounds of the Morse code. This was done in the case where a reporting telegrapher would be in close proximity to a speaker, or any situation where a conventional sounder would be a nuisance. An excellent example of this is covered in "The Era of Morse Telegraphy" by Arthur Grumbine. Arthur covered a speech by President Roosevelt. Art's photo clearly shows several of the special events sets in use.
|View of Western Union Press set-up to cover speech by President Franklin D. Roosevelt Oct 29, 1936, from the steps of the Capitol Building at Harrisburg, Pa. The photo was taken by Arthur Grumbine, whose Morse position is clearly visible in the lower-right-hand part of the picture. 6 of the special events sets can be seen in this photo.|
Just how did these sets work ? The schematic below tells the story.
The line circuit is a very typical mainline relay type 4-C. This is in series with the 2-A steel lever telegraph key. Rather than using a noisy local sounder, a telephone headset powered by 2 D cells works as the telegraph receiver. Using a variable resistor in series with the headset provides a basic volume control. A capacitor across the relay contacts prevents arcing and oxidation of the contacts. Here's a close up of the interior of the set: