Hi Vic, Let's concentrate on (1) because that's where my main intereset is. I bought ANSI/EIA/TIA-464 last year and I got the idea of reverse polarity from this standard itself. The section says that...
--- 4.1.2.3.2 Detecting Far-end Answer Supervision Far-end answer supervision can be provided from some network offices. A PBX may, optionally, use this capability to enhance call accounting features. Following called party answer, the network (where equipped for this service) will reverse the tip and ring polarity on the access line. This reversal will be maintained as long as the connection is maintained and the called party remains off-hook. --- Since this is an American National Standard, I presume that this service should be available in the USA. Maybe I am wrong. I am hoping that someone in TREG can confirm this and perhaps tell me what the US phone companies call this service. Incidently, I am from Malaysia and I've tried to talk to Bell South but they don't seem to know what I am asking for. Can anyone in TREG help me with this please ? Cheers, YH Loke. ---------- From: Victor L. Boersma Sent: Wednesday, 15 July 1998 22:52 To: INTERNET:[email protected] Subject: RE: Question about PSTN Call Supervision in the USA In effect, you have two questions: (1) Call supervision between PABX and Central Office (2) Methodology used in PABX for accounting. The answer to question (1) is not easy but answerable. In effect, it has been answered in two places, the handiest is ANSI/EIA/TIA-464, Private Branch Exchange Switching Equipment for Voiceband Applications. It describes the different interfaces that conceivably could be used. The USA and Canada had many, many telephone companies doing their own thing. That has been whittled down to a manageable number of practices. You may run into anyone of them, as described in the standard. Therer is a second source of Standards on the interfaces from Committee T1. They have a series of standards that describe Interfaces between Customer Installations and the PSTN. There you'll find each interface in a separate standard, such as "Loop-start, Ground-start, Reverse Battery, DS-1, DS3 and such. The answer to question (2) is more problematic in that different manufacturers use different techniques to provide that service in their PBXs. In to-day's digital PBXs there is an added complication in that the owner of the PBX (the Hotel) may have special deals with different long-distance carriers for "least-cost-routing" of calls out of the PBX. It is possible that the interface to Carrier 1, for calls to the North East, is not the same as the interface to Carrier 2, for call to the South West. This is a very specialized area of expertise and the subject does not lend itself well to a quick explanation over TREG. Most of those experts work for the big PABX manufacturers or large consulting firms. The PABX Standard can be ordered from Global Engineering Documents in Denver, Washington, St. louis, Irvine CA, Sydney Aus, Mexico City, Miami, Paris, Hong kong, Tel Aviv or Munich. Let me know what is closest for you and I'll get you the address. I believe that ANSI sells the Committee T1 standards these days, but am not sure. Ciao, Vic
