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.
Test tapes where also made with a repeating RY sequence. This was used by technicians to align the Bias adjustment on equipment such as the 43A1 carrier channel terminal
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*...
The RYRYRY sequence usage can be seen on the following DDH47 weather station broadcast excerpt:
CQ CQ CQ DE DDH47 DDH9 DDH8 FREQUENCIES 147.3 kHz 11039 kHz 14467.3 kHz RYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRY CQ CQ CQ DE DDH47 DDH9 DDH8 FREQUENCIES 147.3 kHz 11039 kHz 14467.3 kHz RYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRY CQ CQ CQ DE DDH47 DDH9 DDH8 FREQUENCIES 147.3 kHz 11039 kHz 14467.3 kHz RYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRYRY ZCZC 643 WWXX60 EDZW 150900 NAUTISCHE WARNNACHRICHTEN VOM 15.09.2017 UM 09 UTC STRONGWIND GALE STORMWARNINGS FOR GERMAN BIGHT AND BALTIC SEA STARKWIND STURMWARNUNGEN FUER NORD UND OSTSEE NO WARNINGS IN FORCE KEINE WARNUNGEN IN KRAFT