|Voice||Live male and female operators|
|Known counterpart stations||M10|
S10 was ran by Czechoslovak military intelligence. This designator refers to the original format from mid 1970s to early 1980s. Around mid 1980s replaced by automated format S10b.
S10 utilized live voice, both male and female, and a musical intro - a taped performance of "Song of the Lark", composed by Pyotr Ilyich Tchaikovsky.
|555||082||555||082||13||28||rovná se, rovná se||79881 79881 89658 89658 ... 43801 43801 43731 43731||rovná se, rovná se||13||28||000|
|3-figure recipient ID||3-figure recipient ID||2-figure number, purpose unknown||Amount of 5-figure groups in the message||"Equal sign"||5-figure paired groups||"Equal sign"||2-figure number, purpose unknown||Amount of 5-figure groups in the message|
|Repeated thrice||Repeated twice||Repeated thrice||Repeated thrice||Repeated twice||Repeated twice||Repeated twice||Repeated twice|
|Repeated for 6 minutes|
S10 often sent more than one message in one transmission to more than one recipient. In that case, in the intro, the ID's were included for all the messages, in the same way as the first one. Then the preamble, the message and the outro except 000 followed for each message. The last message ended the transmission with 000.
Note the use of "rovná se", which stands for the equal sign, and the ending "000". Presumably S10 was a direct conversion from M10. In S10b and later formats these were replaced by "pozor" (English: attention) and "konec" (English: end), respectively.
The Swedish Security Service (SAPO) confirmed the use of S10 by Czechoslovak intelligence, and also published a recording featuring a female operator.
Recording on this page is courtesy of Numbers and Oddities.