user-1: I was hoping to create a cheap security system by connecting an Arduino to the phone line output of a base station.  
Since the base station should call a phone number if the alarm is tripped I wouldn't have to do much hardware hacking so long as I can read/parse the output from the base station.  
My question is can I read serial output from a phone line like this?

user30488: Phone lines run off of the RS-232 telecommunications protocol which can run off -25v to 25v, which would completely destroy your Arduino. Luckily there is an IC made to help you with that. You can use the MAX3232 IC to convert RS-232 to TTL 5v or 3.3v (Same chip can do either). Look at providers like Digikey for just the chip or you can get a breakout from providers like SparkFun.
TL;DR Yes, but you need a special IC to not fry your Arduino.

-1: <p>I was hoping to create a cheap security system by connecting an Arduino to the phone line output of a base station.  </p>

<p>Since the base station should call a phone number if the alarm is tripped I wouldn't have to do much hardware hacking so long as I can read/parse the output from the base station.  </p>

<p>My question is can I read serial output from a phone line like this?</p>
 30488: <p>Phone lines run off of the RS-232 telecommunications protocol which can run off -25v to 25v, which would completely destroy your Arduino. Luckily there is an IC made to help you with that. You can use the MAX3232 IC to convert RS-232 to TTL 5v or 3.3v (Same chip can do either). Look at providers like Digikey for just the chip or you can get a breakout from providers like SparkFun.</p>

<p>TL;DR Yes, but you need a special IC to not fry your Arduino.</p>
