From: utzoo!decvax!harpo!duke!unc!mcnc!jcw
Newsgroups: net.dcom
Title: Re: question on 2-wire phone connections
Article-I.D.: mcnc.1300
Posted: Thu Sep  2 07:04:17 1982
Received: Sun Sep  5 03:15:38 1982

References: mh3bs.185

Your old (or new, for that matter) dial phones will work fine with
red and green (tip and ring in telco parlance) swapped.  However, the
oscillator in the tone pad requires power to operate, and the power must
be of the correct polarity.  The power is obtained from the phone line,
which has a nominal 48 volts DC across it with nothing connected, and
about 24 volts when 'off hook'.  Nothing else in a standard phone requires
a particular polarity, so you can still receive calls on your touch-tone
phone wit the wires reversed.