Slightly diffrent here in the Uk, the exchange uses a 50v supply, so slightly less at the subscriber due to resistance, ringing is 75v ac, and to make the line go off hook a 600 ohm resistance is placed across it.
Also theres a max current for the ringing signal, they call it Ren, ringer extension number, which basically means if you pull more that 80ma while the line is ringing the phone company will think theres a short, and will come knocking.
Also here in the Uk 112 is the same as 999, or 911 in the Us, 112 is easily accidentally dialled when your installing an extension as I found out when the emergency services rang me asking why I'd called them.