Decoding the telephony signals in Pink Floyd’s ‘The Wall’ was a thrilling puzzle that led me to uncover the intricate telephone network signalling used in the 1982 film. Analyzing the audio clip from when Pink calls London revealed a blend of speech, dial tones, rapid tone combinations, ring tones, and more, ultimately encoding the phone number. While DTMF and CAS R2 signalling were ruled out, SS5 emerged as the likely system, matching the frequencies and timing perfectly. By diving deeper into spectrograms and utilizing telecom hardware, the mystery of the number, 044 1831, was successfully decoded, shedding light on the audio production techniques and surprising revelations in other Pink Floyd tracks.
https://corelatus.com/blog/Decoding_the_telephony_signals_in_Pink_Floyd_s__The_Wall_.html