The author pluged the PC soundCard to an oscilloscope .
The author provides the wav file played to do it :
http://mirror.kapsi.fi/koodaa.mine.nu/t ... e-wave.wav
The author says :
if a PC can do that, an Oric can do it too...I programmed a C program to generate it and yes, i have also thought about making some game. Something like asteroids would be a good idea.