|Known counterpart stations||E07, G07, S07, V07, M12, XPA, XPA2, XPH|
XP operated in regular schedules of three identical transmissions, spaced 20 minutes apart. The first transmission could have taken place at any 10-minute interval within an hour. If the first transmission took place before 12:00 UTC, the frequencies of the subsequent repeats increased - otherwise they decreased. If the transmission was too long to fit into the 20-minute frame, it continued, then the subsequent repeat was started as soon as possible.
XP was a 14-tone MFSK system, using two speeds within each transmission - 1 bd for the intro, and 7.5 bd for the message. The following is the list of tones used and their corresponding values, assuming correct tuning:
|2||319||Transmission end tone|
|13||495||Message start tone|
|14||511||Repeat previous tone|
Each transmission goes through several phases, in order: (all at 7.5 bd unless noted)
- 1 bd intro section: 3-digit ID, space (repeat thrice), amount of messages ("000" - no messages, "1" - one message, "2" - two messages), space (repeat all 10 times)
- Tones #14 and #13 alternating 20 times in total, starting with #13
- 10 spaces
- Message: 5-digit groups, followed by a space
- End of transmission: Tones #2 and #14 alternating 20 times in total, starting with #2
When no message was to be sent, the step 4 was skipped.
In the actual messages, the first group always started with "0", and the second group was the amount of groups in the message minus two. Multiple messages were separated by "00000 00000".