Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!apple!bionet!hayes.ims.alaska.edu!accuvax.nwu.edu!nucsrl!telecom-request From: juliet@mhuxo.att.com (Juliet Sutherland) Newsgroups: comp.dcom.telecom Subject: Re: Slick-96 Message-ID: <14871@accuvax.nwu.edu> Date: 20 Nov 90 21:54:13 GMT Sender: news@accuvax.nwu.edu Organization: AT&T Bell Laboratories Lines: 71 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 837, Message 8 of 9 Other responders have accurately described the SLC*-96 carrier system. Here's some additional information that may be of interest to some. The SLC-96 carrier system was the first commercially successful example of a general type of product known as Digital Loop Carrier (DLC) systems. It was introduced in 1978. I have little to add to previous poster's descriptions of it except to say that Mode I can carry non-switched services as well as switched services and that it does not support the bit compression that causes trouble for modems. AT&T Network Systems introduced the SLC Series 5 carrier system in 1985. It is a 96 line, 5 DS1 (including the protection line) system that performs basically the same functions as the SLC-96 system but serves twice as many lines in the same physical space. It introduced a dual channel unit for support of two-wire designed services and provides much better testing and provisioning of non-switched special services than the SLC-96 system. The SLC Series 5 system also supports fiber distribution (that is, fiber from the remote electronics to at or near the customer's house or business). Although SLC Series 5 systems provide DS1 feeder interfaces (that is, DS1 from the CO to the remote electronics), an appropriately hardened fiber multiplexer, such as the DDM-1000 or DDM-2000, is often installed in the same cabinet or structure to provide fiber feeder. The direct (T2?) fiber interface mentioned by a previous poster is no longer sold. The Low Bit Rate Voice (LBRV) configuration mentioned by another poster as a problem for modems, while available on SLC Series 5 carrier systems, has not been widely deployed and should not be a problem for the original poster. AT&T Network Systems has recently announced its newest DLC product, the SLC-2000 access system. The SLC-2000 access system again doubles the density, serving twice as many lines by volume as the SLC Series 5 system. It provides an integrated SONET OC-3 feeder interface, serves up to 768 customers per system on metallic distribution (more on fiber), provides an integral test head to obviate the need for a DC bypass pair for drop testing, will allow up to 8:1 concentration in the remote electronics (but note that it does NOT do local switching) and incorporates many other new features that are probably of less interest to this group. As a previous poster mentioned, the remote electronics (usually called the Remote Terminal (RT)) can terminate on either a Central Office Terminal (COT) or directly on a digital switch. The SLC-96 interface was documented by Bellcore in TR-TSY-000008 and TR-8 interfaces are now available on a number of switches besides the 5ESS* switch. For those who are interested in such things, Bellcore has published a new RT-switch interface specification, TR-TSY-000303, which provides additional capabilities not supported by TR-8. The most notable differences are support for ISDN BRI (think about how one multiplexes 2B+D, it's not obvious), support for larger RTs (TR-8 allows only 96 line RTs), and the potential for improved operations and maintenance. The SLC Series 5 system, the SLC-2000 access system, and the 5ESS switch will all be providing TR-303 interfaces. Finally, for the diehards that have read this far, Bellcore also specifies functional requirements for universal systems (that is, DLC systems that use a COT rather than terminating directly on a switch, called universal since that arrangement will work with any switch) in TR-TSY-000057. TR-57 does not specify the interface between the RT and COT, which may be proprietary, but does specify such things as transmission, signaling, and environmental requirements. I am a systems engineer for these products and will be glad to answer additional questions. *SLC and ESS are registered trademarks of AT&T Network Systems. Juliet Sutherland AT&T Bell Laboratories Whippany, NJ juliet@mhuxo.att.com