In article krw writes:
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In article ,
says...
krw wrote:
In article ,
says...
Mike Tomlinson wrote:
Phone wires were clamped to ground before the 1960s?
It was common to earth one leg of the incoming pair to either the house
ground or to its own rod. An earth connection also allowed "party
lines", where two houses could share one physical phone line pair, each
house with its own number. Disadvantage was that both lines could not
be used simultaneously.
http://en.wikipedia.org/wiki/Party_line_(telephony)
I think they used to ring between the red green for one party, yellow
green for the other party, black green, etc.
No, that would defeat the purpose of the party line. The ringers
either had "distinctive ring" (once for Mabel, twice for Maude) or
were frequency tuned.
They did frequency and distinctive rings. But for 2 parties you can ring
red-to-ground for one and green-to-ground for the other. It is in Mike's
Wikipedia link above. My recollection is black was ground and yellow was
sometimes used for a light in the phone (red and green are phone wires).
Princess phones used the yellow green pair for the dial light. A
transformer was hidden somewhere in teh house to supply the power
(IIRC, a standard 24VAC door bell transformer, but it's been a lot
of years).
6 volts as I recall. I had one of the transformers around ages ago,
it may still be stashed somewhere.
Not sure about the pair, though, since green/red is tip/ring of pair
one, black/yellow is tip/ring of pair two. Putting the transformer between
green and yellow would be putting the light current on the talk pair,
which would be inviting hum on the line.
More modern wiring uses:
colors:
main/stripe
-----------
white/blue green tip 1
blue/white red ring 1
white/orange black tip 2
orange/white yellow ring 2
white/green tip 3
green/white ring 3
white/brown tip 4
brown/white ring 4
( from
http://www.ling.upenn.edu/~kurisuto/phone_wiring.html )
Similarly, I would question the reliability of ring on a single line referencing
ground, since party lines tended to be out longer distances -- the ground resistivity
would make it more difficult to get ring current to the phone(s).
I think the differing ring frequency would make more sense, since mechanical
resonance in the ringer provides a reasonable tuning mechanism.
Alan