In a message dated 96-07-26, David Drori writes: >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?
David: I do not think that the 600 ohm termination is required anymore for receiving caller ID signals. Bellcore included it in their original spec, but in 1993 they decided that it was not necessary (or even desirable). I made a quick check of my files, and I could not find written confirmation of the change in the specification. However, they told me this verbally in August 1993, and said they intended to issue a bulletin to revise the spec. Eliminating the requirement to switch the AC impedance makes the design of the hardware and software somewhat easier. If anyone on treg has more info on this subject, I'd like to know. I haven't paid much attention to this issue since 1993, so my information may be out of date. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc.
