Bwanna can you check into this.

[Dan/Panther]

I have heard from more than one source that the phone system is not polarity senssitive, and really makes no difference.
Can you find out the 411 for us and put this to rest once and for all.

I personally have connected modular plugs from the wall to the phone regardless of orientation of the wires, which would switch polarity if not connected the same each time, yet I have never encountered a problem.
I'm really confused as to this issue, and would like to know for sure.
Personally, I don't think they are polarity sensitive.
I may be wrong but would like to kmow for sure, one way or the other.
D/P

[JorgeAmely]

If an early TT phone does not have a bridge rectifier inside, it will be polarity sensitive.

[dsk]

Phones approved to be used in Norway shall not depend on polarity.
Some years ago (40) we had some coin phones witch used changed polarity to collect the coin.

dsk

[bwanna]

d/p   phones today are not polarity sensitive. an old party line set would need correct polarity. typically on house wire red=ring (battery); green=tip (ground). newer house wire will be white/blue, white/orange; white/green, with the white being tip side.

of course, there is always the chance telco has reversed things in the field or CO, too.  if you have an ohm meter, you could check.

a little off topic, but i connected the third conductor of my premise wire to ground &  in the jacks. my pty2 phones will ring without moving any wires inside the phone.

jorge, show us a pic of a bridge rectifier, please.

[bingster]

Here's a rectifier bridge, Donna:

[JorgeAmely]

Donna:

Rotary phones are not polarity sensitive, because there are no electronic components that need to be biased in a particular way for the phone to operate. Bias is like the way you connect a battery to your car: negative to ground and positive to the starter, otherwise, many electronic components will be damaged.

Early Touch Tone phones needed to be biased (or connected) in a particular manner, otherwise, the electronic components for the buttons would not operate correctly. That is solved with the use of a bridge rectifier or a polarity guard.

Click here to see a sample of a polarity guard:

http://www.ericofon.com/catalog/parts/pg.htm

It is just made of four diodes arranged as a bridge rectifier. These rectifiers are very common in all kinds of appliances we interact with every day. Your car alternator has three, every simple wall wart may have one. Everywhere where you have AC current that needs to be rectified into a small DC power supply most likely has one.

[Dan/Panther]

Donna;
What is the voltage coming into the house. AC, DC, or pulsating DC.
D/P

[Dennis Markham]

Good one Bingster, got a kick out of your photo of the rectifier bridge. 

[Dan/Panther]

Bingster;
Is that a blue ST tube? Arcturus ? I've never seen a blue ST tube, Mine is a globe.
I thought that in that configiration, it was a Trestle Rectifier, and not a Bridge Rectifier.
D/P

[bingster]

It's actually not blue.  It's a run-of-the-mill clear Sylvania, but the only photo I could find had it sitting in front of a piece of blue fabric, which gives the tube a blue tint.

[Dan/Panther]

I was going to offer you $100.00 for it.
D/P

[bwanna]

thank you, jorge 

you too, bingster, but i think d/p is correct. what you have is a trestle rectifier

d/p, the line is 48v dc current/ ringing current is ac.  are you just testing me

[Dan/Panther]

thank you, jorge 

you too, bingster, but i think d/p is correct. what you have is a trestle rectifier

d/p, the line is 48v dc current/ ringing current is ac.  are you just testing me

Donna;
Why or course not, if I were testing you, I'd ask how tall the average telephone pole was, or how many pegs for climbing are there, on each side of the pole ?
Then again, I think you probably use the basket nowadays.
D/P
However I'm a little confused at the voltages. With only two wires in my phone system from the pole, how do they get AC, and DC at the same time ?

[JorgeAmely]

D/P:

At rest (phone on hook), there is -48 Vdc on a phone line. It is negative to prevent erosion of the copper lines.

When the phone rings, the central office sends you about 90Vac at 20 Hz to ring the bells. When you pick up the phone, DC current is drawn by the phone (transmitter is inserted between L1 and L2 by the hook switches); the central office senses the current consumption, stops the ringing voltage and drops the voltage to -5 to -9 Vdc to sustain the 20-30 mA of current required to operate the phone.

When the phone rings, the 90 Vac are superimposed on the -48 Vdc.

Direct TV and Dish Network do something similar to power their amplifiers and receive the signal from the satellites over a single cable. Your box sends DC to supply power to the amplifier, the amplifiers send the 1+ GHz signal on the same cable simultaneously to your receiver. The receiver uses a simple capacitor to stop the DC and allows the AC from the satellite to be processed for your TV.

As you say in the news ... "the phone is a remarkably complex, [yet] simple device ..." 

Those old engineers were really smart.

[Phonesrfun]

Good question!

Because there is DC on the phone all the time, and ringing current only when the central office wants to tell your phone to ring.

They actually superimpose the AC ringing current right on top of the DC.  That way, the ringer rings when it gets the AC ringing current and the DC is there to sense the fact that you have picked up the phone to tell the central office to stop ringing.  This is done over the single pair of wires.  They figured out how to do this way back in the early days of central offices.