US ringing voltage varies somewhat but generally ranges from 86VAC to 105VAC 20 hz, again depending on the distance of the line from the central office. With new technologies available now which extend the virtual central office presence out farther (Subscriber loop carriers), the ringing voltage is generally kept at the low end, as the need to drive the long loops is not as much of a factor anymore.
In the US, the 2 line leads are referred to as "Tip" (voltage return), and "Ring" (-48vdc). These terms have their origins in the old cord board operator consoles of days gone by. The patch cords used were simular in size and shape to the large stereo hedphone jacks today. If you look at the jack, you see it is divided into 3 sections. First is the tip of the jack, next is a section that resembles a finger ring, and third is what resembles a long shirt sleeve. Thus the terms "Tip", "Ring" and "Sleeve" were used to refer to the 3 main leads used in early electro-mechanical switching systems.
Ringing voltage is generally applied to the "ring" lead of the line pair (-48vdc side) with the following exceptions.
In the case of 2, 4, and 8 party lines, the parties ringing voltage was applied to either lead depending on the party designation of the number. Parties 1,3,5, and 7 were designated "Ring" parties and parties 2,4,6,8 were "Tip" parties, with the ringing cadence applied to the appropriate line lead. The telephone sets for party lines were modified by the installer to connect the internal ringer circuit to the correct side of the line for ringing detection. This modification allowed only 1/2 of the parties on any line to hear the ringing cadence at any given time. The pre-determined cadence of short and long ringing bursts (4 and 8 party only) was applied to the line and the users had to determine which party should answer the phone. I do not think there are any more multi-party lines (with the possible exception of 2 party lines) available in the US anymore, but it makes a good history lesson anyway.
Dialtone