Governments use them to send messages to naughty spies in the field.I suppose they have those weird interval tones as something distinctive to tune in to.
en.wikipedia.org/wiki/Lincolnshire_Poacher_(numbers_station)
(en.wikipedia.org/wiki/Lincolnshire_Poacher_(numbers_station)
hoifbjifbef,
Mon 7 Nov 2011, 22:16,
archived)