M10 was run by the Czech Military Intelligence (Czech: Vojenské zpravodajství). Morse code counterpart to S10d. Active since mid 1970s (multiple formats) until 20 June 2007.

Format: (post-1990)

M10's intro, preamble and outro were sent at 15 WPM, while the message groups were at 20 WPM. Zero was sent as T - a single dash. M10 often sent more than one message in one transmission to more than one recipient. In that case, in the intro, the ID's and the group counts were included for all the messages, in the same way as the first one. Then the preamble, the message and the outro except "0 0 0" followed for each message. The last message ended the transmission with "0 0 0".

From 1990 to 2006, the arbitrary ID was only 555. Then from 2006 until the station's demise random triplets were used, but never 555.

M10 had a large amount of schedules at all times of day, which outnumbered those of S10d. On many schedules, the messages were usually first sent in the morning, and repeated later in the evening. M10 could have started at any 5-minute interval within an hour, and was usually, but not always, transmitted on two frequencies in parallel.

From the early 1980s until 1990, M10's format was slightly different - M10c. M10's format in 1970s was very similar to the last one - see S10.