An early experimenter of the limiterless RTTY demodulators, Robert Weitbretch himself deaf, also invented the TTY (telephone teletype) for the hearing impaired, together with the invention of the acoustical coupler for landline modems.
Robert Weitbrecht operated for a number of years as W9TCJ when he worked at Yerkes Observatory.
Mr. Weitbrecht passed away in 1983. His picture appears on the cover of the book A Phone of Our Own — The Deaf Insurrection Against Ma Bell by Harry Lang. A biography of R. H. Weitbrecht appears here.
"What is this Two-Tone Detector?" RTTY Bulletin, September 1963. (Reprinted in the January 1964 Issue.)
This is the first amateur article that highlights the frequency diversity property of limiterless demodulation.
"The W6NRM Radioteleprinter Terminal Unit, Mark V." RTTY Bulletin, September and October 1965.
This Terminal Unit includes a "Mark-Space Frequency Diversity through the incorporation of Two-Tone detection techniques." Weitbrecht had incorporated the experimental limiterless detector which he had used in his earlier TUs into this new TU.