From comp.dcom.telecom.tech 107 Path: ucbvax!dog.ee.lbl.gov!agate!howland.reston.ans.net!spool.mu.edu!news.clark.edu!netnews.nwnet.net!news.uoregon.edu!gaia.ucs.orst.edu!ruby.oce.orst.edu!jackson.lambda.com!scott From: scott@jackson.lambda.com (Scott Statton N1GAK) Newsgroups: comp.dcom.telecom.tech Subject: What's a channel bank/T1 Message-ID: <9312160203.AA00490@cluon.jackson.lambda.com> Date: 16 Dec 93 02:03:42 GMT Organization: University Computing Services - Oregon State University Lines: 73 NNTP-Posting-Host: ruby.oce.orst.edu Originator: root@ruby.oce.orst.edu In a recent posting someone asked some simple T-1 questions, and there was some misinformation posted. T-1 is the generic name for a 1.544 Mbps signal. It can carry 24 voice-grade channels, or 24 56k circuits. Primary rate ISDN uses the same signalling and bit rate, but has it's own framing (i.e. there are 23 'clear channel' signals, and one signalling channel). A T1 is usually synonymous with a DS-1. (The differences: some people use T1 only when referring to 4-wire copper pair engineered loops, and DS1 when referring to any T1-speed signal, i.e. a single DS1 within a DS3 on a fiber) Some terminology to get you started: Channel Bank: A device that demultiplexes the 24 channels and makes them available. Your canonical Wescom D4 channel bank can be loaded with FXS cards (looks like a telephone line) FXO cards (looks like a telephone set) DSO cards (provides digital interface, suitable for your 56kbps circuits) and a few others not seen to much any more (like circuits to implement ring-downs, dial-pulse repeaters, etc.) Expect to pay around $5,000 for a fully equipped channel bank from any of the used telecom vendors. Cheap ones can be had for less, but you definitely get what you pay for. Newbridge makes a series of channel banks that are pretty cheap, but cannot be configured as nicely. If you're smart, you can find D4s for sale at a great price. CSU/DSU: 1. This is a device that is used as the demarcation point on a T-span. It provides Loopback functions (for remote testing) and isolates the ~+130 Vdc used for powering repeaters. Some newer equipment designed to use T-1s comes with built-in CSU/DSU. (like the US Robotics 2*T1 to 48*RS-232 automatic modem thing, very sexy .. now they just need a TCP/IP terminal server ... ) These should cost around $350 to purchase, I'd guess. Brand names are the T-serv II by Kentronics. 2. This name is ALSO used for the terminal device that demarcs a 56kbps circuit. Nicer ones (like the Codex 4000 series) will do sync/async conversion, and speed conversion. Allows you to use a single channel of your t-span to carry data at popular baud rates. Has a 4-wire interface on one end, and an RS-232 and/or V.35 interface on the other). Typically $200 to $400. DACS: This is a device that will take a handful of T-spans and rearrange channels within the span. An example is the Fredericks' Engineering microDACS. This which can be had used for about $6,000 will allow you to take four spans (minimum configuration) and re- arrange them. Suppose you have a PBX that is T-1 capable, and you have a router that is T-1 capable, but the PBX won't handle fractional T1, and you want 12 channels of the span to go to the PBX, and the other to hold data. One would configure the DACS to split the span in two, and keep them off each other's backs. You probably won't need one of these, but you might. Q: Why do I need TWO channel banks? A: One for each end. Some LECs will provide channel banks at zero, one, or two ends when providing DEF (Digital Entrance Facilities). if you're getting DEF from a digital switch (DMS-100, ESS-5, Stromberg DCO) they shouldn't need one at their end. If you're getting it from an analog switch like an ESS-1A, then they'll need one at the office. If you've got more questions, email me direct, and I'll summarize the salient parts to the net. Scott Statton -- network engineer, Applied Signal Corp From rec.radio.amateur.digital.misc 849 Path: ucbvax!agate!howland.reston.ans.net!vixen.cso.uiuc.edu!qualcomm.com!network.ucsd.edu!news-mail-gateway From: ka7oei@uugate.wa7slg.ampr.ORG Newsgroups: rec.radio.amateur.digital.misc Subject: Scrambler lockup Message-ID: <38403@uugate.wa7slg.ampr.org> Date: 11 Dec 93 05:55:25 GMT Organization: ucsd usenet gateway Lines: 33 NNTP-Posting-Host: ucsd.edu Originator: daemon@ucsd.edu Here in Utah, we have designed and run some test on a T1 radio modem. The modem appears to work very well but there is an area of slight concern: This modem uses a 17 bit maximal-length scrambler (taps on bits 5 and 17). This scrambler uses the same circuit topography as the scrambler in the GRAPES modem and uses 2 XOR gates (74HC86) 2 shift registers (2 74HC164's) and a flip-flop (1/2 of a 74HC74). The problem seems to be that there some unsusal circumstances (cause unknown) in which the scrambler seems to get "stuck". Since this sequence generator is obstensively an open loop system (as opposed to a PN generator used for Spread Spectrum) I don't see how this should be able to occur, but occur it can. Has anyone else had experience with this sort of scrambler and had to deal with this problem? Several things come to mind: On could detect the lack of appropriate transitions and reset the system to get it working once again. One could also have the system software detect a stoppage of the data and cause a reset to be issued. Interestingly enough, the descrambler, which is nearly identical to the scrambler, does NOT seem to exhibit this sort of behavior. We will soon be using these modems in a full-duplex T1 microwave link and will report on their performance. ka7oei@uugate.wa7slg.ampr.org clint@uugate.aim.utah.edu From comp.dcom.telecom.tech 183 Path: ucbvax!cis.ohio-state.edu!magnus.acs.ohio-state.edu!math.ohio-state.edu!howland.reston.ans.net!spool.mu.edu!news.clark.edu!netnews.nwnet.net!ogicse!flop.ENGR.ORST.EDU!gaia.ucs.orst.edu!ruby.oce.orst.edu!philabs.Philips.Com!add From: add@philabs.Philips.Com (Aninda Dasgupta) Newsgroups: comp.dcom.telecom.tech Subject: Updated summary of T1 equipment with modem banks etc. Message-ID: <9312161914.AA06104@philabs.Philips.Com> Date: 16 Dec 93 19:14:44 GMT Organization: University Computing Services - Oregon State University Lines: 194 NNTP-Posting-Host: ruby.oce.orst.edu Originator: root@ruby.oce.orst.edu [This is an updated version of a summary I posted a few weeks back. This article has more recent information obtained from USRobotics. Also, it gives a "vanilla" solution using DACS and channel banks. For those who are not familiar with T1 terms and equipment, there was a nice article on the TeleTech mailing list (perhaps also on Telecom Digest) by scott@jackson.lambda.com (Scott Statton N1GAK) on Wed, 15 Dec '93, that explained some of the T1 terms and equipment.] A number of people from the net asked me to forward whatever information I have received regarding equipment needed to connect 24 modems to a T1 line. Below I have described the main features of each. All this information is what I have assimilated from market-speak and brochures of the vendors. Summary of my application's needs: I want to provide two kinds of services to my geographically distributed salespeople; both services are to be provided from a workstation-based server. Service 1: Salesperson dials in from his laptop and on my end I want to dump some ASCII and graphics messages on his laptop screen - pretty much like a remote terminal server. Service 2: Salesperson dials in from a POTS telephone, uses DTMF keys to choose a service and gets messages played back and/or a fax sent to a fax machine - very much like voice-mail systems, banks offering credit card balance information and fax-back systems. I need the two services to be served off one workstation because the information accessible via the two services (using modems or telephone sets) is identical and because I want to aggregate my incoming lines onto a single T1 so that I can get good LD rates from my LD provider. Vendors that have products that allow offering such services are listed below. 1) US Robotics - Total Control WAN Hub ----------------------------------- This product is offered as a chassis and various options on cards. They have a dual-T1 card with drop-insert capabilities, frac. T1 enabled, accepts ANI/DNIS and requires no external CSU. The DSP-based quad-modem cards have built-in fax-modem (V.32bis) capabilities, can access DNIS, can load DNIS-dependent modem configuration, will (someday) route the data to LAN adapters (instead of RS-232 ports) and can originate and terminate fax/modem calls. USR also talks about making LAN adapter cards (Enet and TR) available in late '94, which will allow direct connections to a Token-ring or Ethernet LAN. They will also have a LAN Gateway card that will work in conjunction with the LAN adapters to route data to/from the quad modems to the LAN. TCP/IP and X.25 will be initially supported on the Gateway cards, and Appletalk, etc. will be added later. Any application specific protocol of your choice can be downloaded onto the Gateway card. This will allow you to use any home-brewn protocols for transactions, data exchange, etc. between remote applications. A terminal server card will be avialable around mid-'94. Voice cards (with RJ11 output, I guess) will be available "later '94." USR will also have ISDN PRI, X.25 and Frame Relay cards that go in the same chassis. The chassis and most of the cards are controllable/monitorable using SNMP, either from a PC (with software available from USR) or from any other SNMP host on the LAN. Some of the cards are also controllable via RS-232 dumb terminals. For more (and perhaps accurate) information, contact US Robotics at (800) 342-5877. I spoke with Michael Cashman, Ext. 5636 (Marketing/Sales). I also spoke with Don Balton - (708) 982-5091 who used to head the group that designed this product, and Lauri Lentz in Public Relations. 2) Primary Access -------------- I found out about Primary Access from, among others, its founder, Jim Dunn. They are reachable by email. They seem to have a larger installed base of their product as compared to the USR product described above. This prouduct is also a chassis based system. The single-T1 card has drop-insert capabilities, is not capable of frac. T1 (from what I could gather from their glossies), needs an external CSU (but only for loop-back testing) and accepts ANI/DNIS. However, the ANI/DNIS is accessible to a host computer only if you use an X.25 link between the chassis and the host. This means, in order to get the ANI/DNIS, you need to buy an X.25 card for the chassis and an X.25 card and software for the host. The dual-modem cards are V.32bis compatible, can do DTMF decoding, can originate and terminate modem calls, and they promise routing of modem data to LANs within the next year. These cards don't seem to be as feature rich as the USR cards (e.g. on the fly, DNIS-dependent configuration download, etc.). They offer X.25 cards and Frame Relay too. Network management is done using CMIP. All software on the cards can be downloaded for upgrades. Voice call support is provided using their 8-port FXS cards (something that is lacking in the USR offering at this time). They have promised Ethernet support in about a year. They assured me that they can price their products very aggressively. For more information call: (619) 536-3000 Fax: (619) 693-8829 3) Dialogic -------- This is a all-in-a-PC solution. Dialogic offers a T1 interface card for the IBM PC bus. This card provides access to ANI/DNIS, has drop-insert capabilities and requires an external CSU for loop-back testing. They have various versions of the T1 card, offering various options for the number of T1 ports. Also offered is a PC-based four-channel Voice card that does DSP-based call processing. Combined with Dialogic's voice-processing software (PCM encode/decode API) and DTMF recognition capabilities, this card provides an excellent way to implement voice-based services. Dialogic also offers fax boards that will allow you to send out faxes from the PC. The PC, equipped with a LAN adapter card can, via the application software route all data to a network. I am not aware of network monitoring features (SNMP or CMIP). Also missing is any V.32bis modem capabilties. One attraction of going the Dialogic way is the elimination of any cabling which is needed to connect the USR or Primary Access products to any host system (e.g. RS-232, twisted-pair etc.). All the cards use Dialogic's PEB bus for internal data transfers. For more information call Dialogic Sales and Technical Support: (201) 334-1268. 4) IBM's CallPath Line of Products: ------------------------------- IBM offers a uniform API to interface to phone systems, independent of the the PBX vendor and the host system platform. e.g. one could use the same programs to implement CallPath-based applications on MVS, AS/400, OS/2 and AIX based systems and interface to PBXs from Rolm, NT, etc. One requirement is the PS/2 based CallPath SwitchServer/2, which seems to be a system that has hard-wired links to the PBX and sits on the LAN and serves all requests for operations from the CallPath host. The host to SwitchServer link is supported using SNA LU6.2 (yuk!!). They support DID, DNIS, CLID, ANI etc. and have T1 boards for the RS/6000 (I am not aware if they have boards for the PS/2 and mid to main frame systems, but I assume they do). Although an interesting product with a seemingly rich API to perform all kinds of call routing etc, the main drag is the PS/2 requirement to interface to a PBX (what if I don't have a PBX?) For more information call: (800) IBM-CALL and ask for information on CallPath line of products. A Vanilla Solution using DACS, Channel Banks and CSU/DSUs -------------------------------------------------------- An alternative to all the above solutions, and perhaps much more messy (in terms of writing purchase orders and cabling), is to use a CSU box to terminate the T1 span. Then, use a DACS+Channel Bank to do the splitting of the lines into modem and voice calls. However, I am not sure how one would use two 800 numbers - one for modem calls and one for voice, and somehow have the DACS recognize the DNIS and split them accordingly. Do they make DACS or Channel Banks that will use DNIS to split the DSO channels? (I bet they do.) After the Channel Bank, the modem lines would have to be fed into v.32bis modems. This might create a nasty cable spaghetti between the Channel Bank and the modems. Besides, buying and managing 24 or 48 modems is expensive, right? Then of course there is the cabling from the modems to the host's serial ports. I have seen a Wireless RS-232 box that transmits to 500 ft. But I don't know how 24 of them would perform sitting next to one another. The advantage of this solution is that you can buy used equipment for cheap (there are plenty of used telco equipment vendors) and get something up and running. [The following sources were mentioned in an article by scott@jackson.lambda.com (Scott Statton N1GAK)] Channel Banks: Newbridge, Wescom DACS: Fredericks' Engineering CSU/DSU: Kentronics, AT&T etc. Summary and Wish List: --------------------- The Primary Access and USR offerings both look attractive. I wish Primary Access delivered ANI/DNIS without X.25. I wish both USR and Primary Access had LAN adapters for their chassis so that I wouldn't need to run 24 RS-232 cables from the modem cards to my workstation. (Getting a workstation equipped with 24 serial ports is quite difficult.) The Dialogic product can be neatly packaged in a PC, but I don't trust a PC to do my important call processing and service providing functions. And Dialogic doesn't provide V.32bis modem-banks in their PC solutions. Finally, I wish the IBM product didn't need a PBX and a PS/2 to interface to it. Disclaimer: ---------- I DO NOT GUARANTEE the accuracy of any of this information. As I said, this is what I have understood or guessed from whatever information I was able to gather directly from the vendors. I might have misunderstood some deficiencies, or unknowingly embellished some features. If so, that was unintentional. If anybody familiar with these products finds any inaccuracies, I'd appreciate being told about it. If anybody knows of any other such products, I would like to hear about them too. Thanks to all those who responded to my queries on this (and other) mailing-list(s). Aninda ------------------------------------------------------------------------------- Aninda DasGupta (add@philabs.philips.com) Ph:(914)945-6071 Fax:(914)945-6552 Philips Labs\n 345 Scarborough Rd\n Briarcliff Manor\n NY 10510 "Err.., Phillips Petroleum gives you gas; fortunately Phillips Chemical makes antacid. Philips is with one "el", we make lightbulbs. And other shtuff." From comp.dcom.telecom.tech 467 Path: ucbvax!cis.ohio-state.edu!math.ohio-state.edu!howland.reston.ans.net!spool.mu.edu!olivea!news.bu.edu!att-in!att-out!cbfsb!cbnewsf.cb.att.com!deej From: deej@cbnewsf.cb.att.com (david.g.lewis) Newsgroups: comp.dcom.telecom.tech Subject: Re: Questions on current technology and CSU/DSU's Message-ID: Date: 22 Dec 93 14:44:59 GMT References: Sender: news@cbfsb.cb.att.com Organization: AT&T Lines: 51 In article storkus@netcom.com (Mike Storke) writes: > Just how is telecom traffic routed through fiber? I know that WTCI's > microwave system (used by Allnet, and possibly as a backup by Sprint) > uses 4 channels of 135 MBPS each. I also know that you can modulate > laser diodes upwards of 1 GHz. A co-worker who used to work at Xerox > (I'm still not sure what Xerox and telcos have to do with each other) > says that even long distance companies don't send more than 250 MBPS, > which translates (from a table I saw somewhere) to around T4 (DS-4) speed. > So is this true or what? Maybe a techie from one of the big three > (AT&T, MCI, or Sprint) can tell the net? Current fiber optic systems use one or two pairs of fibers. One fiber in each pair carries traffic in each direction. If two pairs are used, one is a "service" pair and one a "protection" pair. (They're sometimes referred to as "primary" and "secondary", just to confuse things - which means you can never abbreviate the designations of the fiber pairs, because if you write "P" and "S", the "P" pair could be the "primary" pair or the "protection" pair... but I digress...) Current systems I know of work at the following rates (rates given are those available for user traffic and don't include overhead inserted on the optical side of the system): 1.544Mb/s (DS1) (e.g. AT&T FT1) 6.32Mb/s (DS2) (e.g. Telco Systems FOX-2) 45Mb/s (DS3) (e.g. Telco Systems 828AF) 51Mb/s (SONET/SDS OC1) (e.g. Fujitsu TM-50) 90Mb/s (2*DS3) (e.g. AT&T DDM-1000) 135Mb/s (3*DS3) (e.g. ... can't recall) 155Mb/s (SONET/SDS OC3) (e.g. AT&T DDM-2000, Fujitsu ADM-150) 180Mb/s (4*DS3) (e.g. AT&T DDM-1000) 417Mb/s (9*DS3) (e.g. AT&T FT Series G 560Mb/s (12*DS3) (e.g. Telco Systems M560) 565Mb/s (SONET/SDS OC12) (e.g. AT&T FT-2000, I think) 1.7Gb/s (36*DS3) (e.g. AT&T FT Series G) 2.4Gb/s (SONET/SDS OC48) (e.g... don't know) There's also an FT Series G that provides 3.4Gb/s by wavelength division multiplexing of two 1.7Gb/s systems, but that's only used where fiber is scarce. Examples are just pulled from the surface of my memory and are not meant to imply any endorsement of particular products or vendors... except, of course, for the AT&T ones, which are far better than any others... ;-) Disclaimer: I never designed any of this stuff, I just used it in a former life. David G Lewis AT&T Bell Laboratories david.g.lewis@att.com or !att!goofy!deej Switching & ISDN Implementation Copyright (c) 1993 David G Lewis/AT&T; all rights reserved