priyom.org

Protocol

XPA2 utilizes a proprietary 16-tone MFSK waveform at the speed of 7.8125Bd, and the shift of 15.625Hz. Each tone represents one character:

Hz Character
1000.000 Space
1015.625 (Not used)
1031.250 Start of message
1046.875 End of transmission
1062.500 (Not used)
1078.125 Repeat previous character
1093.750 0
1109.375 1
1125.000 2
1140.625 3
1156.250 4
1171.875 5
1187.500 6
1203.125 7
1218.750 8
1234.375 9

Broadcast procedure:

  1. Precisely two minutes of 400 ms of the 9 tone (1234.375Hz), and 1600 ms of the space tone (1000Hz) repeating.
  2. The tone string 6666622662626 (forming continuous tones).
  3. The repeat and start of message tones alternating (20 tones in total).
  4. 10 space tones (continuous 1000Hz tone string).
  5. 5-digit groups, each separated by a space.
  6. The end of message and repeat tones alternating (20 tones in total).

Messages in form of "0#### 00001 00000 10140" are null messages.

One broadcast can contain multiple messages. The messages are separated by "00000 00000".

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