On Aug 10, 10:56*pm, wrote:
On Sun, 10 Aug 2008 18:19:49 -0400, "Marilyn & Bob"

wrote:
I believe that the old rotary phones were 3 wire, not two. *

That was for selective ringing on a party line. Just hook the green
and yellow to the green on the new jack. Red to red.

Yes and no:

In most cases and on a single party line the 'third wire' allowed the
'ringer (electromechanical bell inside phone or sometimes even
separate) to be connected, or not connected as required.

The above posting is correct that on 'some' party lines the ringing
was sent on one side of the line (with respect to ground) for, say,
one party on a two party line and other side of the line for the other
party!

There were also other other systems of ringing; including multiparty
coded ringing (two longs and short etc.) which also sometimes used one
side of the line or the other.

And ringing systems that used different frequencies of ringing; there
was on for example (Sold by AECo. Chicago), that allowed for five
different ringing frequencies, 16, 25, 33, 50 , 66 cycle/hertz etc.
and with those five frequencies on each side of the telephone line it
was possible to have up to ten parties on one line. This was usually
on long rural lines; but am familiar with one city that used to have
four parties on a line, using the different frequency ringing. That
city did not use ringing to ground (i.e. one side of the line because
of the difficulty, in that rocky and high resistivity of the soil
location, of obtaining and maintaining good ground connections! So in
that instance the four (not five) frequencies were sent on the pair of
wires, not in respect to ground.

The advantage being that only one party's phone would ring on an
incoming call; thus allowing a 'little more' privacy!

ALL OF WHICH: Leads to another comment/suggestion to the original
poster:
If you wish or have trouble getting your 'vintage' phone to ring on
incoming calls (and you wish to have it so) check that the ringer/bell
is connected either by that third lead or internally inside the phone.
Also if it is of some non North American manufacture it 'may' have
been designed to work best on some ringing frequency other than the 20
hertz most commonly used in North America; however recollection is
that the non frequency selective ringing phones are usually not that
sensitive to ringing frequency and would sometimes ring (continuously
or intermittently) when power faults came in contact with telephone
lines.

Strikes one that there must have been as many varieties of phones
around the world since Alexander Graham, a Scottish immigrant to
Canada discovered the principle of turning speech into variations of
electric current, as the many versions of radios/wireless sets in use
since the advent of radio transmission.