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M13

Enigma ID M13

Name
Frequencies
Status Inactive
Voice N/A
Emission mode ICW
Location Bulgaria
Activity pages

Known counterpart stations E18, G22, S04

M13 belonged to one of Bulgarian intelligence agencies. Morse code counterpart to E18, G22, S04. Last heard in early 2006.[1]

The transmission format is given below. The speed was 12 words per minute, and one dash was used for zero.

Preamble Message Repeat Outro
458 BT 195 20 BT 95404 17097 16052 ... BT 458 BT 195 20 BT 95404 17097 16052 ... BT Three long dashes
3-figure ID   Serial number Amount of 5-figure groups in the message   5-figure single groups   3-figure ID   Serial number Amount of 5-figure groups in the message   5-figure single groups   "0 0 0"
Repeated for 5 minutes             Repeated for 1 minute              

The serial number was increased each time a new message was sent on a given schedule.

M13 was significantly more active than its voice counterparts. M13 transmitted every day, and constantly changed times and frequencies. All the transmissions took place in the 00:00-10:00 and 16:00-23:59 time frames. The average message length was 23 groups. The messages were repeated in one of the following patterns:[2]

  • On the same day, 1 hour later, on the same frequency
  • On the same day, 1 hour later, on a different frequency
  • On the next day, at the same time, on the same frequeny
  • On the next day, at the same time, on a different frequency

References

  1. ENIGMA Control List, Revision #25 [accessed September 18th, 2014]
  2. Numbers & Oddities #4 (July 1998) [accessed September 18th, 2014]
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