Trapping modem indicators.

[Hans]

I was just wondering: is it possible to trap modem indicators and if so,
how? E.g. I would like to know when a modem puts the line in OH (off hook),
trap that signal and use it in a script (or Tx and Rx signals for that
matter). /proc doesn't seem to have it and the modem-HOWTO neither.
Pointers appreciated. --Hans