[Asterisk-Users] how can i connect a cost display on asterisk

[Jorge Alayon]

In my country payphone solutions for Call Shops are implemented using FXS
SIP or H.323 gateways that implement the Polarity reversal feature that
reverse polarity as soon as the other party answers. I have done this in
several VoIP platforms but Asterisk.

Regular Payphones and Call Shop metering systems rely on polarity reversal
for proper call billing implemented in a local table.
Call Shop uses mainly a central billing unit (a PC or stand Alone) and
serveral metering boxes with display that connects to the central unit by
RS485 bus.
These boxes connects to the lines (FXS on the gateways or special payphone
lines provided by local carrier) and to normal phones.
a Call Shop can have form 2 to 16 call boxes. It it good bussiness above 8.
Billing systems are so simple electronically that they are manufactured
here. 

Regards,

Jorge A.



-----Mensaje original-----
De: abuse at cabal.org.uk [mailto:abuse at cabal.org.uk]
Enviado el: Miércoles, 06 de Abril de 2005 11:01 a.m.
Para: asterisk-users at lists.digium.com
Asunto: Re: [Asterisk-Users] how can i connect a cost display on
asterisk


<ht at phonitel.com> wrote:
> Johannes,
> I would be curious to know if there is a solution for this. Another
> solution is that you buy a "call meter". Which is a small box that
> can be placed in front of phone phone and that can display costs.

> FXS--> call meter --> analog phone

> This call meter needs to be programmed with a table inside and a
> rate for each destination.

It depends on the type of cost meter. One of BT's products is the
Meter Pulsing Facility which sends a short 50Hz longitudinal tone on
supervision, and just before a "unit" has been consumed. BT scrapped
unit charging in the mid-90s but this particular bit of legacy
remains. It's intended for payphones where you charge, say, 10p for a
unit and want to know when the 10p has been consumed.

That's why you can sometimes hear a buzz on a BT payphone a few
seconds before the credit drops, because the longitudunal pulse
sometimes breaks through into the audio path, even though shouldn't. I
suspect this is because they payphone isn't properly earthed.

A cost meter (or paypgone) that determines cost without exchange
assistance will suffer from inaccurate pricing information and an
inability to determine the start of supervision. Still, given that BT
charge a hefty wedge for the MPF, some people just stick a COCOT on a
standard exchange line and hope it's good enough that they don't get
ripped off.

-- 
Common sense is the collection of prejudices acquired by age 18.
							- Albert Einstein
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