|Enigma ID||X06, X06a, X06b, X06c||
|Emission mode||USB + carrier, USB, AM|
|Known counterpart stations|
Mazielka is a selective call system used by the Russian MFA and/or intelligence. It is a USB + carrier (H3E), less commonly AM (A3E) or USB (J3E) mode transmission of a 1998 ms 6-tone string, 333 ms per tone, followed by a 1380 ms pause, repeated. The strings can be written as numbers mapping to the following approximate frequencies:
Typically, strings of only unique digits are sent, allowing 720 unique combinations. However, fewer than 30 are actually being used. A Mazielka broadcast can last anywhere between a few seconds and a few hours. Many transmissions are heard on semi-fixed schedules, on specific days within specific time frames.
Sometimes transmissions are made, which may consist of sequences such as 121212 (an alternating two-tone X06a sequence), 111666, 111111 (consecutive-repeat X06b sequences) or 123456 (the X06c sequence). These can extend for many hours.
The Mazielka system has been used since 1970s. It used to be closely affiliated with diplomatic RTTY and Serdolik broadcasts, and even earlier - with the number station XPH. Its current purpose is uncertain. The sequence 111666 is sent about an hour before scheduled transmissions of E07, M12, XPA, and XPA2.
Until the early 1990s, some broadcasts were made with a high pitched tone between the tone strings, instead of a pause: