Dear Treggers, I was surprised not to find any replies to the following query from Peter Van Raalte, dated August 18, 1995. I have similar questions, and need to specify timing for product software that needs to detect and interpret caller ID information. Also:
1. Where can I obtain the Bellcore spec quickly? Is there a Web site with free access to specs? 2. Is there an equivalent Canadian spec? Where can it be obtained? 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. 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. 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 -----------------------------------------------------------
