Number Station 

Stations left over from the cold war that broadcast numbers. To transelate these numbers, you would need a one-time translator issued by the station's goverment directly to their agents. After being used once the code for the station is changed, -as suggested by the name-, and they are burned. Number stations are not avaible to the public, but everyone somehow manages to record it and upload it to youtube or something.

So, am I the only one who thinks Mason listened to a LITTLE too many number stations? Just maybe, a LITTLE?

Number Station by TheDailyFail December 29, 2010

cuban number station 

It is not known exactly what they are there, but its pretty much transmitted enigma in CW mode and then a bunch of numbers (in Spanish) in AM mode. It sounds like a female computer voice.

Cuban number stations can be monitored all across North America.

CUBAN NUMBER STATION COMMON JAMMING FREQUENCIES:

3060 (very common on the 6.6 MHz pirate radio band also)
3090
3292 6867 7648 8790 11215
3410 6872 7682 8873 11468
3444 6888 7726 8980 12144
3926 6890 7743 8992 13373
40176892 7755 9120 13419
4020 6920 7845 9140 14180
4027 6933 7860 9237 14736
4174 6935 7887 9251 14770
4601 6983 7890 9255 14825
4610 6953 8010 9330 17425
4328 6942 8018 9925 17520
4479 6768 6995 8066 10125 18035
5087 6778 7425 8126 10180 18434
5118 6787 7435 8136 10270 20316
5135 6797 7480 8150 10345 21865
5407 6800 7482 8165 10510
5415 6825 7520 8186 10713
5417 6840 7525 8240 10865
5420 6856 7580 8380 11125

cuban number station by IrishRepublicanArmy December 10, 2003