pdf 60jan BSTJ p235 - Pushbutton Callilng with a Two-Group Voice Frequency Code Popular

Published on 12 April 2020 919 downloads

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By L. SCHENKER. "A customer voice-frequency pushbutton signaling scheme involving a new two-group signal code, termed "four-by-four", is described. It is shown that the use of this code, with judiciously chosen frequencies, permits the detection of bona fide signals after transmission over any ordinary voice connection and facilitates discrimination against false signals resulting from speech. Apparatus for generating the tones is described, and the principles of reception are discussed." Contributed by Paul Fassbender.

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