Hey hey,
I have just put together a little UDO that encodes numbers into EuroSignal. EuroSignal was an old paging system up to 1997. It played special tone patterns on the low ultra shortwave band around 87.3-87.4 MHz. You could hear these earie unmelodic tone sequences on normal radios, if you went completely to the left of the scale.
https://www.dropbox.com/scl/fi/5sq21syrsby9uosad42s0/eurosignal.zip?rlkey=bh59jai4o1n72z5096fs3cfoe
For the longest time I had mistaken these tones for something to do with emergency services radio. -- Anyway: it comes with a UDO and a demo file. It's dead easy to use and written according to the specification as found on Wikipedia. A link is included in the UDO.
This is on Dropbox, so will vanish after a while. I'm still in the process of reorganising miscellaneous Csound code into a permanent form.
Best wishes and enjoy,
Jeanette