The Swedish Counter Intelligence Säkerhetspolisen (SÄPO) has recently published a story about a Swedish double agent who was the recipient of S10 Bulgarian Betty, an old Czechoslovak number station.

totoCZ comments:

What's interesting is that it's read live, and uses "=" (Equal sign, "Rovná se") instead of "Attention" (Pozor). The shortwave number stations legend, Jochen Schäfer, has confirmed he remembers hearing this old version in the late 1970s.

We've heard a similar recording of S10 like this one before and we can guess the first format of the station was a direct conversion from the CW version - which probably started earlier than in the late 70s.

We've contacted S Ä PO and they told us this is the only recording that's available (for now, I would assume).

The original post by SÄPO and a Swedish news article are not available in English, luckily Wizard2 has provided us with a translation.

http://www.sakerhetspolisen.se/ovrigt/pressrum/aktuellt/aktuellt/2015-01-23-lyssna-pa-ett-hemligt-telegram.html

http://www.svd.se/nyheter/inrikes/sapos-hemliga-radiotelegram_4273023.svd

Listen to a secret telegram

What did a secret spy telegram sound like during the cold war? We have been digging in our archive - and we found a Swedish double agent.

You can listen to what the secret telegram sounded like here

The use of encrypted radio messages was for a long time a common way for communication between the client and the spies. Alf, a co-worker at säkerhetstjänsten (literally security agency) since 1981, gives some backstory to just this secret message.