RY (test signal)

RYRYRYRY... is a character string that was widely used to test a five-level teleprinter or RTTY channel. The characters R and Y are "01010" and "10101" in 5-bit ITA2 code, also known as Baudot. Thus they are Boolean complements of each other.

Switching between the two characters is a stressful test for electromechanical teleprinters.[1] Repeated over and over, RYRYRYRY... outputs a carrier wave that regularly and rapidly shifts back and forth in frequency.

This signal pattern also provided a test for signal polarity; if polarity was reversed, the test signal would print as "SG".[2]

The corresponding string of complementary characters in 7-bit ASCII is U*U*U*U*...

References

  1. ↑ An Introduction to Amateur Radioteletype p.10
  2. ↑ Digital Signal Types
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