Note
QST, Nov 1932, p. 78.
Shortwave Craft, Nov 1932 p. 407
Shortwave Craft, Nov 1932, p. 428
Shortwave Craft, Nov 1932, p. 433
QST, Mar 1935, p. 105 (improved)
QST, May 1935, p. 118
Radio Amateur's Handbook, 20th edition (1943), p. 73
The Teleplex system of Morse code training was predicated on the idea the that a person could best learn the code by listing the code he or she had just sent. Teleplex machine were designed to record a student's sending and then play it back. Over the years, the technology Teleplex used to accomplish this changed several times.
The first machine (Figure 1), introduced n 1932, recorded the operator's sending by applying ink marks on copper tape that correspond to the dots and dashes sent. During playback, the ink marks provide non-conductive areas on the tape which interrupted the flow of current, triggering an oscillator. Presumably then, the tapes could be wiped clean and reused. The variable speed drive mechanism that pulled the tape through the machine was wound with a crank. The tones made during operation were made with a battery powered 3-volt vacuum tube oscillator.
While the improved Master Teleplex (Figure 2), introduced early in 1935, was still spring wound, dots and dashes were embossed on the tape, rather than inked. Ad copy said, "no more fussing around with ink tapes, no more relays, no more complicated battery hookups, no more fading signals." The reference to "no more complicated battery hookups,” implies that the machine had some kind of built-in power supply. This version also added a "bug" style key, which Teleplex called "Telespeed," described as an "unbelievably smooth automatic key."
A still later version (Figure 5) from around 1942 is also a "plug in" model requiring no batteries. Ad copy states "no perforations, no ink." Marks on paper tape (Figure 6 and 7) were made using a "refillable pencil lead." Playback was most likely accomplished with a photoelectric tube.
References
"Boy Scouts Learn the Code." Radio News, Dec 1932, p. 338. (the 1932 Teleplex machine is used in this article, and includes some details on how it works)
