W8SDZ@SIMTEL20.ARPA.UUCP (07/19/86)
The 20-30 software updates that were scheduled to be made to the Northern Telecom DMS-100 switch (which were supposed to solve the problems of garbled modem connections) were done in the Southfield Michigan exchange ESS office. Now, instead of 2 out of 3 calls being garbled, it's about 1 out of 3 - certainly an improvement but still more to go. About two weeks ago Michigan Bell changed several more ESS offices in the Detroit area to Northern Telecom DMS-100 digital switches, including the one where my RCP/M system is located. This has resulted in numerous complaints from my modem callers about garbled connections. Even from my home, which is only one exchange away, about one out of three calls to that system result in garble problems at 1200 or 2400 bps. Some 300 baud callers report being unable to connect at all and others say they lose the connection during their session. That phone number was previously on a crossbar switch. A Michigan Bell employee who asked not to be quoted by name said that the Royal Oak office (a major hub center for the suburbs) was slated to have a DMS-100 installed soon and Michigan Bell has decided to put that switch in another office of less importance. He went on to say (this is unsubstantiated) that Michigan Bell has cancelled all future orders with Northern Telecom for DMS-100's and will instead in the future be using Western Electic digital switches. He also said that in order to fix these problems they are going to have to lock all the oscillators in the various digital switch frames together to a common master oscillator, and further that they are going to have to lock all the exchanges to a master oscillator at some central point. Another source told me that he has heard that 70% of ALL digital switches being installed in ESS offices in the U.S.A. are Northern Telecom DMS-100's. Looks like modem users are in for it. We'll probably have to change the technology of modems to make them ignore the discontinuities caused by the 8 kHz switching in these digital switches. --Keith Disclaimer: I have no proof that the above is true, only the word of sources that I trust. Tests I have personally made, however, did track down modem garble problems at work to the DMS-100 digital switch in the central office. The problems disappeared after I got them to change that phone number over to a crossbar switch.