atcomsystems.ca/forum Forums General General Telephone & Systems Information reverse polarity

I was thinking more in general terms than specifically the link between a SxS end office and a tandem.

A distant tandem would still need to signal answer supervision back over carrier to the first tandem where the CAMA functions were being carried out. Just wondering if with SF that was based purely upon removal of the return-path 2600Hz supervisory for a predetermined time.

Paul,
While I never really messed with the CAMA trunks, I would think the billing would kick in at the local switch when a connection would be determined to be established. It would have nothing to do with the SF that was on the long haul portion on the trunks. While the trunk was seized there was no SF. That's why some older women with high voices would talk themselves off the line.

Dear all moderator, admin & other members, sorry my rudeness not giving full profile, just updated.

Thanks all for replaying, so much very deep technically explanations here I don’t think I can get it much :p lol

How about in early day pay phone?

I just founded this meaning “support reverse polarity” cross by my reading in commercial payphone website, just knew that used for public payphone, but not sure about it. Some of them said "Reverse Polarity" is a kind charging signal for the public payphone, when a user is using a public payphone, there will be charging signal such as pulse (16 kHz or 12 kHz) or reverse polarity sent to the payphone, so that the payphone can calculate the amount the user consumed.

A "reverse polarity" is the polarity opposite to the current polarity, for example, if the current polarity is positive, then the reverse polarity will be negative.

The "reverse polarity" is used for charging the money for the user. When the user makes a call through the payphone, and when the call is connected, a signal is sent to the public payphone, and then the payphone starts charging the money for the user. So "so that the payphone can calculate the amount the user consumed" means both time and money the user consumed.

The charging signal is specially applied for the public payphone lines (especially for the unattended outdoor type public payphone), the normal lines for home or office does not have such kind of charging signal.

Other said the reverse polarity is answering pulse (Signals or Binary code/message), it sends from Exchanger network. It use for billing start sign on the payphone business wire line or wireless line.

So can I summary that “reverse polarity” used for billing method for payphone?

More likely, I'd say that it was/is generally used to indicate that a call has been established and conversation can/has begun. It would probably be useful for any call that was chargeable to the calling station, be it payphone, or private line. Can I get a confimation on that rash statement? John C. (Not Garand)

If it does'nt work, REVERSE EM'!(again) :thumb:

But how does the local switch which is performing the CAMA function know when the connection has been established if answer supervision is not returned over the long-haul trunk somehow?

Say somebody made a call from an end office in Georgia to an end office in California and the call went via tandems in Atlanta and Los Angeles, with the Atlanta tandem handling the CAMA/billing for the smaller Georgia C.O.

Surely the end office in California must return answer supervision to Los Angeles, which in turn must signal it back over the carrier system to Atlanta? Without that, how would Atlanta know that a call has been answered and that billing must commence, rather than the call just ringing, going to intercept, busy, etc.?

I know that applying 2600Hz in the forward direction (i.e. calling end to called end) reset the trunk, but I'm not sure about the reverse direction. i.e., could the call above be something like this from the point of view of the long-haul trunk:

1. Atlanta seizes trunk to Los Angeles by removing 2600 supervisory.

2. (Optional perhaps). Los Angeles acknowledges by a "wink" removal of 2600 in the return direction but then keeps the tone on for now.

3. Atlanta sends KP + number + start to send number.

4. When Los Angeles receives answer supervision from the end office (e.g. by polarity reversal on D.C. trunks from SxS) it removes the 2600Hz which Atlanta then recognizes as the signal to start billing.

At the end of the call, of course, Atlanta then releases the trunk by applying 2600Hz in the forward direction and Los Angeles acknowledges by re-applying 2600 on the return path to show the trunk as being vacant.

That's how I could see it working, obviously with 2600Hz filters on the incoming trunk at Atlanta so that ring, busy, intercept recordings can be heard by the caller without the loud tone being present.


1.

Now this will really mess you up ..... CAMA timing. Assumed billing. ???

Try NEAX CAMA ....

Now then, obviously we are off the topic, we have defined the question, it has been encapsulated by the questioner, so ...ENUFF!!!!

If you would like to continue this conversation, please do so via PM or e-mail. Thank you.

You’re statement is over simplified… In that case the “reverse polarity” would signal to “start billing” … but a “polarity reversal” or “wink” has a few different uses for trunk signaling.

The most common use of Wink-Start (reverse polarity) is in PBX trunks… The battery source swaps polarity (i.e. pos/neg on tip/ring) to signal things like “ready for digits” or “call in progress.”