stacy@sobeco.com (s.millions) (01/04/91)
Well, I finally got the cisco pancake routers I have been waiting
for. Now, for my first batch of silly questions...
I want to test these things before they get installed (call me
crazy, but this is my first experience with routers and V.35). My
problem is, how do I connect the two beasties together? Is it
as simple as a V.35 null modem cable? Do I need one of these V.35
modem eliminators that I see advertised? Could I do the same
job with a V.35 break out box, they seem to be as expensive as
the modem eliminators, but provide a little more info (I might not
know what is going on, but I like to _see_ what is going on :-).
-stacy
--
"Sorry I had to plug you mister duck, but I'm a sportsman." stacy@sobeco.com
- Almyer Fudd uunet!sobeco!stacylars@spectrum.CMC.COM (Lars Poulsen) (01/05/91)
In article <1991Jan4.145007.22904@sobeco.com> stacy@sobeco.com (s.millions) writes: >Well, I finally got the cisco pancake routers I have been waiting for. > >I want to test these things before they get installed (call me >crazy, but this is my first experience with routers and V.35). My >problem is, how do I connect the two beasties together? >Do I need one of these V.35 modem eliminators that I see advertised? Yes. As in any other synchronous serial modem interface, the question is "Who supplies the clock?", and the answer is "The modem does". >Could I do the same >job with a V.35 break out box, they seem to be as expensive as >the modem eliminators, but provide a little more info (I might not >know what is going on, but I like to _see_ what is going on :-). The V.35 breakout boxes tend to be expensive because they need to have a power supply to drive the lights. V.35 uses a differential signal with less than 1 Volt drive. I never understood why the phone companies liked it so much when we already had RS422 which had +-5V drive which is enough umph to drive lights directly and even to interoperate with RS232 in a pinch. But you still need somebody to supply the clock. -- / Lars Poulsen, SMTS Software Engineer CMC Rockwell lars@CMC.COM
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) (01/06/91)
In article <1991Jan5.062616.7340@spectrum.CMC.COM> lars@spectrum.CMC.COM (Lars Poulsen) writes:
-V.35 uses a differential signal with
-less than 1 Volt drive. I never understood why the phone companies liked
-it so much when we already had RS422 which had +-5V drive which is
-enough umph to drive lights directly and even to interoperate with RS232
-in a pinch.
V.35 predates RS422 by maybe as much as 10 years.
Marc Kaufman (kaufman@Neon.stanford.edu)fortinp@bwdls56.bnr.ca (Pierre Fortin) (01/06/91)
In article <1991Jan4.145007.22904@sobeco.com>, stacy@sobeco.com (s.millions) writes: > > Well, I finally got the cisco pancake routers I have been waiting > for. Now, for my first batch of silly questions... > > I want to test these things before they get installed (call me > crazy, but this is my first experience with routers and V.35). My > problem is, how do I connect the two beasties together? Is it > as simple as a V.35 null modem cable? Do I need one of these V.35 > modem eliminators that I see advertised? Could I do the same > job with a V.35 break out box, they seem to be as expensive as > the modem eliminators, but provide a little more info (I might not > know what is going on, but I like to _see_ what is going on :-). Your not crazy, you'd be surprised how extensively we test all equipment which goes on our network; sure gets a vendors attention when they are not allowed to have their equipment connected until they fix any major non-conformance problems... :^} With V.35, I highly recommend you test with the _same_ cables you plan to install in the field. No, you can't just make up a null cable; you _will_ need a modem eliminator. Better yet, if you plan to use T1, use the CSU/DSU itself; you'll be surprised to find that 1.544M will *not* work due to T1's one's-density requirement. The break-out boxes are handy, but now that cisco has gotten the V.35 interface straight, these shouldn't be necessary unless you've got a physical problem. Oh yeah: get high quality cables. We've resorted to designing our own which gave us slightly more than 10dB improvement in noise/crosstalk immunity. Our cables have individually shielded pairs with an overall shield. The pair shields are grounded (drained) at the signal-source end only. The outside shield is grounded to the cisco and the modem. This may seem like overkill, but if you had seen the problems we suffered through a year ago with our older cables, you'd understand why I CUT (really) any old cable I find *anywhere* (stockroom, parts cabinet, etc.) If you really like to _see_ what's going on, then you'll want a V.35 datascope (up to sub-rate T1) of some sort. Full T1 datascopes are rare beasts however. > > -stacy > Good luck! Cheers, Pierre Fortin Bell-Northern Research I know, my postings are Internet Systems P.O.Box 3511, Stn C terse and humourless. So? (613)763-2598 Ottawa, Ontario RIP: aptly named protocol fortinp@bnr.ca Canada K1Y 4H7 AppleTalk: Adam&Eve's design