Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!texbell!vector!telecom-gateway From: chip@vector.dallas.tx.us (Chip Rosenthal) Newsgroups: comp.dcom.telecom Subject: Re: Putting A Call On Hold Message-ID: Date: 9 Sep 89 22:35:06 GMT Sender: news@vector.Dallas.TX.US Reply-To: chip@vector.dallas.tx.us Organization: Dallas Semiconductor Lines: 43 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 364, message 3 of 5 ssc-vax!clark@beaver.cs.washington.edu (Roger Clark Swann) writes: >X-TELECOM-Digest: volume 9, issue 360, message 3 of 7 > There was a news story I saw over a year ago where a US West spokes person > was asked about the newer features such as caller ID, call block, call > trace, selective forward and so on. The person replied that US West was > looking into the features but that they didn't think they were viable in > today's market place.... > OoooK... < US West is one of the greatest impediments to the modernization of the phone system. While the rest of the country is moving forward with a new set of standards (ESF framing, B8ZS line coding, etc.), US West is digging in their heels trying to maintain their investment in obsolete equipment. If you ever try to get a piece of T1 equipment into the US West area, you will come up against a strange beast called ZBTSI. This non-solution addresses the issue that a T1 line conveys the timing in the data, and data is represented by pulses. Long strings of zeros mean long intervals with no pulses, and the repeaters can lose track of the timing. The preferred solution is to use a line coding technique called B8ZS which replaces eight consecutive zeros with a special code word containing a pulse pattern which does not occur in normal traffic. The receiving equipment recognizes this code word and restores the eight zeros. Older equipment not only lacks the ability to support B8ZS encoding, but goes so far as to munge it beyond recognition. The US West non-solution is a technique called ZBTSI which pre-empts the T1 facilities data link, normally used for network control and status monitoring, and requires storage and processing of the data on a frame by frame basis. This kludge is totally incompatible with existing standards and future ISDN capabilities, impedes the ability to do useful things with the facilities data link, and reduces call quality by introducing significant processing delays. The spokesman is right, these advanced calling features aren't viable. But it isn't because of any lack of demand, it's due to obsolete network equipment. (It goes without saying, but I'll say it anyway: these are just my personal opinions.) -- Chip Rosenthal / chip@vector.Dallas.TX.US / Dallas Semiconductor / 214-450-5337 Someday the whole country will be one big "Metroplex" - Zippy's friend Griffy