KEVIN.GRIFFIN@ehpcb.wlk.com (KEVIN GRIFFIN) (11/13/90)
Can anyone tell me what a "Slick 96" switch is and what kind of services are available from it. One of my local (SWB) techs told me that one is about to be installed in my local exchange, but he didn't want to tell me anything about it. Kevin Griffin
djo@pacbell.com (Dan'l DanehyOakes) (11/17/90)
In article <14710@accuvax.nwu.edu> KEVIN.GRIFFIN@ehpcb.wlk.com (KEVIN GRIFFIN) writes: >Can anyone tell me what a "Slick 96" switch is and what kind of >services are available from it. Actually, that's "SLC-96," for "Subscriber Loop Carrier." It's a digital carrier designed to carry [up to] 96 lines ("conversations") or the equivalent to a distribution point farther from a Central Office than the usual limit for local loops. Basically you can do anything with it that you can do with an aggregator of digital (or digitized analog) lines. The Roach
BRUCE@ccavax.camb.com (Barton F. Bruce) (11/17/90)
In article <14710@accuvax.nwu.edu>, KEVIN.GRIFFIN@ehpcb.wlk.com (KEVIN GRIFFIN) writes: > Can anyone tell me what a "Slick 96" switch is and what kind of > services are available from it. One of my local (SWB) techs told me It really is SLC 96. Subscriber Line (Carrier? or Concentrator?) Think of a T1 channel bank like device designed to be stuck out on a concrete pad in the boonies (-40C to +65C rating), or in the cellar of an urban high-rise. Think of it as remoting a piece of the CO out on the end of some digital facilities. It can handle single and multi party, coin, VF special services, and up to 56kb data. Can use copper T1s, or fiber at T2 (4xT1). It operates in three modes. Mode I uses four T1s to 96 subscriber ckts (full availability) with an optional 5th T1 hot standby. The single + multi party plug-ins are two ckts per card, thus filling the box. Mode II Concentrated config. Uses two T1 (48 ckts) with an optional third T1 hot spare to serve 96 subscribers with a fixed 2:1 concentration for single and multi-party lines. In this mode it can also support up to 16 special service circuits that are NOT concentrated, and their ckts are one per card. Mode III Special services ONLY using two T1s with optional third T1 spare. The 48 possible ckts, at one per card fill the system. Perhaps you would care to order the doc + practice set: 700-546 SLC-96 Documentation and Practices - seems to be only $3.25 (may be typo) in a distributor's catalog. The Schematics are: # 700-548.
kravitz@ucsd.edu (11/19/90)
In Volume 10, Issue 823, Message 4 of 12, Keven Griffith asks about Slick 96. SLC-96 means "Subscriber Loop Carrier-96" and it is a method of digital multiplexing to accomplish "pair gain". The remote end of SLC-96 is a box which is mounted in the field. The box has an AC operated power supply and gel-cel storage batteries. For each 24 subscribers, it uses two pairs back to the central office. Thus 96 subscribers are supported by 8 pairs. Usually there are two spare CO pairs brought in for good measure. The pairs run at T1 rate (1.544 MB/Sec). It is possible to run with 1/2 the number of CO pairs, but then you can't give everyone service at once. If the office is an analog office, another box like the one in the field converts the eight pairs back into 96 pairs. If the office end of the setup is a #5 ESS (any size), the digitally multiplexed lines connect directly to the switching equipment. Forgive the pun: it is very slick. There was an entire Bell Labs Technical Journal dedicated to SLC-96 in December of 1984. It is Volume 63 Number 10, Part 2. Any large engineering library (university) should have it. Jody
tnixon@uunet.uu.net (Toby Nixon) (11/20/90)
In article <14710@accuvax.nwu.edu>, KEVIN.GRIFFIN@ehpcb.wlk.com (KEVIN GRIFFIN) writes: > Can anyone tell me what a "Slick 96" switch is and what kind of > services are available from it. One of my local (SWB) techs told me > that one is about to be installed in my local exchange, but he didn't > want to tell me anything about it. As was noted in a previous reply, a Subscriber Loop Carrier system is not a switch. It provides a digital connection (often fiber optic) from the switch out to a neighborhood, for example, and then standard analog two-wire connections from the SLC to your residence. Unfortunately, some SLCs (slicks) are decidedly NOT "slick". Modem manufacturers get complaints about modems not working, and often find that the problem is a SLC having been installed. The cause usually is that the SLC is using ADPCM (compression), which doesn't work well with high-speed modems (particularly V.29 [Group 3 fax]). SLCs also are known to introduce analog impairments in the loop that can cause problems for modems, even though they're not audible to voice callers. Most SLCs don't cause problems, however, so there should be no cause for immediate concern. But in response to your question -- there's no "services" from a SLC; as far as you're concerned, it's a passive device. Toby Nixon, Principal Engineer | Voice +1-404-449-8791 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net
juliet@mhuxo.att.com (Juliet Sutherland) (11/21/90)
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
forrette@cory.berkeley.edu (Steve Forrette) (11/21/90)
Another problem with these "concentrators": most do not pass the CPC signal upon disconnect. According to a friend who works for US West, the one specifically called "Slick-96" does deal with this, but the others don't. Apparently, it is quite a problem when they cut existing lines over to one of the ones that doesn't handle CPC -- they get all sorts of calls "My answering machine just runs and runs, and doesn't detect when the caller hangs up like it used to." US West's attitude seems to be that it is not a "supported feature" of their service. If it works, great! But if it stops one day, you'll just have to do without.