>Date: 26 Jul 96 02:58:44 EDT >From: David Drori <[email protected]>
David, >1. Where can I obtain the Bellcore spec quickly? Is there a Web site with free >access to specs? You can obtain the specs (there are several of them that you need to read) from the Bellcore web site. Bellcore makes money by selling their copyrighted standards, and they are not available for free. >2. Is there an equivalent Canadian spec? Where can it be obtained? Bellcore is pushing this "standard" of theirs worldwide, and they deliberately didn't submit it to any of the national or international standards bodies. One reason (they say) is because it takes so many years to get a standard approved through normal channels (like EIA/TIA or ANSI/ITU-T). The U.S. and Canada use the Bellcore standard, as do many other countries. >3. How long should subscriber's equipment wait after the end of the first ring >before placing the 600 ohms termination on the line and searching for caller ID >data? Since distinctive ringing may be combined with caller ID, how is software >supposed to decide that a double or triple ring is complete before placing the >600 ohm termination on the line and looking for caller ID data? Presumable the >product needs to wait for a sufficient minimum period after the end of the >first ring to preclude the possibility of the second or third burst of the >first ringing cycle arriving during the detection period. However, we need to >ensure that we do not start detecting too late, otherwise we may miss data. I recently posted the three distinctive rings in use in North America, from a Bellcore standard: LSSGR TR-TSY 000506, Issue 3, "Signaling, Sections 6.1 to 6.4" These include (all On/Off times in seconds): Type On Off On Off On Off ---- --- --- --- --- --- --- 1 2.0 4.0 2 0.8 0.4 0.8 4.0 3 0.4 0.2 0.4 0.2 0.8 4.0 Note that Type 2 and Type 3 are actually the "distinctive" rings; Type 1 is "normal" ringing. Also note that these distinctive ring cycles were chosen specifically to make it easier to design a ring detect circuit for Caller ID or whatever. Their "broken" ring cycle on-time is the same as the on-time of a standard ring, i.e., 2 seconds, and all three types end with a full 4 second off-time. So, the data for a Caller ID burst will always occur in the first 4 second off-time, after 2 seconds of ringing, either steady or interrupted. >4. What is the recommended time (governed by the latest specified caller ID >window) and latest permissible time (governed by the timing of the second >ringing cycle) allowed for disconnecting the 600 ohm termination at the end of >the caller ID transmission window - we need to avoid placing a 600 ohm load on >the line during the second ringing cycle. I don't have the Bellcore ADSI specs handy, but obviously it has to be back off by the end of the 4 second off time, before the next on-time occurs. I believe that the Caller ID data burst is less than a second, so it will be over long before the end of the 4 second off-time. - John -------------------------- >The following is Peter Van Raalte's letter of August, 1995, which did not (as >far as I know) engender any public replies. > >"> TREG'ers, >> >> Automatic Number Identification information is transmitted after the first >ring >> burst. Bellcore TR-NWT-000030, clause 2.3.1 says that the first burst is >> 0.2-2.2 seconds long. >> >> Can someone tell me if the real tolerances on the first ring burst are any >> tighter in the US and Canada? (I am concerned only with analog, 2-wire >> loop-start lines from a central office.)" > >Best regards, > >David Drori > >----------------------------------------------------------- >Novarex Enterprises Ltd., >POB 2833, >306-6, Mevo Hapartisanim Street, >Jerusalem 91028, >Israel. >Tel: +972 2 810995 >Fax: +972 2 813750 >----------------------------------------------------------- > > ------------------------------------------------------------------ John Combs, Senior Project Engineer, Inchcape Testing Services Email: [email protected] URL: http://www.testmark.com ------------------------------------------------------------------
