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Why has the 500 / 2500 ringers 2 separat windings on the same coil?

Started by dsk, December 18, 2010, 05:10:28 AM

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dsk

We now the it is like that, but this has been designed like that by some reason. Probably not to make it more expensive. All diagrams I have seen they are connected i series, together with a capacitor. the capacitor is either wired between the two windings, or before one of them. The result is the same, a well working 1 REN ringer.

I have an idea of someone has been smarter than me. (here too  ;) )

dsk

Phonesrfun

dsk:


The reason was for ANI, which stands for Automatic Number Identification.  This was a clever way that the Bell System used to identify which party on a party line was placing a call.  The coil is simply used in series on bridged ringing for a single party line.

On a party line, the ringer would be wired differently so that there would be a ground reference wired to either end of the coils, and ringing current would be placed on either the tip side to ground or the ring side to ground on incoming calls.

Since each side has different resistances, the toll equipment could sense this on an outgoing call and determine which number to charge for a call.

This eliminated the need for intercept operators to have to come on the line and ask you what number you were calling from before letting the call you had just dialed go through.

In the case of a line with more than three parties, or if the equipment could not get a clear reading of the party, or in the case where the subscriber's central office was not equipped with ANI, the intercept operator was still needed.

Obviously, this is all a moot point these days, since party lines are a thing of the past.

I believe the Bell System was the only company that used this method in a large scale.  Stromberg Carlson and ITT also made phones with the split ringers.  Since they were supplying independant companies with phones, it is possible that the independants began using this method too.  AE was famous for using a dial that inserted an extra pulse at a particular point in the dial wind-down to achieve their version of ANI.  These dials were called SATT dials, and I am at a loss to remember what SATT stands for.

I don't think the split coil method was ever used in Europe.  I think Europe used the SATT or other methods.
-Bill G

dsk

Thank you for a detailed and understandable explanation.  :)

I guess you are correct regarding Europe. Here in Norway (as far as I know), they used fixed cost on local calls, and manual long distance until the carrier frequency equipment became common in the 1970-ies. The monopoly was political squeezed to limited service. In "my stairway" in the apartment building 2 of 7 had phone until 1974 when the 3rd got one. Quite common to receive calls for the neighbours, and run to get them to the phone. 
How would this be today?  8)

dsk

Adam

My humungous GTE Station Installation and Maintenance Handbook to the rescue again!

SATT stood for Strowger Automatic Toll Ticketing.

According to my book, there were two kinds, SATT Type A and SATT Type B.  As far as I can tell from my book, Type A added one OR MORE additional pulses, Type B only added one additional pulse.
Adam Forrest
Los Angeles Telephone - A proud part of the global C*Net System
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