Rec. ITU-R F.342-2 1 - sigidwiki.com
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WEBITU-T Recommendation U.20 (Fascicle VII.1) gives the signalling conditions to be used when telex communication is to be established by means of such radio circuits: 9.3 signal β should normally be transmitted to indicate the idle circuit condition. However, for signalling purposes, the signals α and β may be employed.
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