First heard in December 2003, the XPA numbers station is a MFSK digital mode station operated by the Russian SVR. Formerly used the 20 baud rate, but now only uses the 10 baud rate (see below for 20 baud sample). These tones can be decoded with the software Rivet.
XPA always has two more broadcasts afterward, each being 20 minutes apart. XPA will also usually send out test tones. Prior to its broadcast, it will also send out a fluttering-like sound (also shown below).
XPA Sample Recording
Waterfall Samples
| Message Tones | Transmitter Sound |
 |
 |
| Test Tones | |
 |
XPA using the 20 Baud Rate, Recorded by Token
Tone Functions
| 520 Hz – Low Start Tone | 600 Hz – Low Sync Tone |
| 720 Hz – End Tones | 760 Hz – 0 |
| 800 Hz – 1 | 840 Hz – 2 |
| 880 Hz – 3 | 920 Hz – 4 |
| 960 Hz – 5 | 1000 Hz – 6 |
| 1040 Hz – 7 | 1080 Hz – 8 |
| 1120 Hz – 9 | 1160 Hz – Message Start Pulse |
| 1200 Hz – Repeat | 1280 Hz – Start High (Used With Start Low) |
Station Structure
1.) 2 Minutes of high and short pitches lead-in tones
2.) Message sync tones
3.) 3 Digit ID (###)
4.) Messages Follow, includes more sync tones every 64 groups of 5 numbers
Null Messages have ID 000 and always sends 0#### 00001 00000 10140
Numbers Station Summary
Name: Polytones
Activity: Active
Emission Mode: USB (Formerly AM)
Country of Origin: Russia
Related Stations: E07, G07, S07, V07, M12
