The "GSM shield" (https://www.stavros.io/posts/irotary-saga/#:~:text=GSM%20shield https://www.stavros.io/posts/irotary-saga/#:~:text=GSM%20shi...) link target w

The "GSM shield" (https://www.stavros.io/posts/irotary-saga/#:~:text=GSM%20shield https://www.stavros.io/posts/irotary-saga/#:~:text=GSM%20shi...) link target was likely hijacked, you might want to replace it with a snapshot (https://web.archive.org/web/20150524if_/www.gsmlib.org/ https://web.archive.org/web/20150524if_/www.gsmlib.org/).