When party lines are discussed, people usually talk about coded
> ringing and that everyone's phone rang with all calls.
> However, in city service this did not occur.
> The panel dial switching system, developed in 1922, included
> provisions for two and four party line service, which were common in
> those days. Each party had their own listed phone number and could be
> anything, not necessarily consecutive. There was no need for party
> letters. When calling a party line, the switchgear deteced the type
> of selective ringing and (bias and ground combinations) and sent out
> the appropriate ringing current. Only the desired telephone rang.
> This helped privacy since other parties wouldn't know the phone was in > use.
I'm not sure what the invention of the Panel Type office has to do with coded ringing on party lines. There were millions of SxS connectors that were wired for terminal-per-station ringing, and full-selective four-party ringing was the norm.
Two-party lines were almost universally full selective, using tip or ring to ground to cause the property party to ring.
Four-party full selective ringing could also be provided in terminal- per-line SxS offices, but there were many drawbacks to terminal-per- line operation.
Wes Leatherock snipped-for-privacy@aol.com snipped-for-privacy@yahoo.com