James@FSU.BITNET (James Messer) (12/01/88)
I have recently acquired an ARK LDM-4 Modem which is manufactured by Electronic Products Inc. Since the modem was bought second hand, I have no documentation for it. No cables were supplied for the modem, and the only phone jacks for the modem are four screws in the back which say TX and RX. I'm assuming that a phone cord can be connected here, but which colors match each screw? After that can be determined, how can I make the modem "pick up" on the phone line? So far, I've failed at everything. Any suggestions would be appreciated. Please reply to JAMES@FSU. Thanks! James Messer James@FSU.BITNET
joel@arizona.edu (Joel Snyder) (12/03/88)
In article <8811301805050FA.GUWI@RAI.CC.FSU.EDU> James@FSU.BITNET (James Messer) writes:
asks about the ARK LDM-4.
This is not designed to work with the PSTN; the LDM-4 requires a
dedicated copper-only (LATA) 4-wire circuit between the two points
you want to connect. This is slightly different from a V.29-type
modem, which requires an LADA type of circuit. I'm not sure about
the phone company in whatever city you're writing from, but you probably
can get a LATA circuit between your home and office for only a few
dollars a month, assuming that you live a mile away or less. For
some reason, the LATAs seem to have been glossed over in the pricing
war to make data users pay through the nose---in Tucson, I can get
an LATA in the same CO for $20/month.
I don't have the latest information on ARK modems here, but there's
a fifty-fifty chance the modem you have is synchronous only as well,
which means you'll need to make sure that your home and office equipment
are matched to talk synchronous (hint: most aren't).
On the bright side, we use ARK short-hauls (LDM stands for "Limited
Distance Modem") at 14.4 over local loops all the time, and they work
great! Every six months, you have to tweak the pots in the front
to bring it back into coordination with the one on the other end, but
it's sturdy gear.
Joel Snyder
PS: I know that an LADA circuit is a 3004, or 2 of the 3002. But is
there a common nomenclature for LATA circuits? It usually takes
3 to 4 people before I can find one who knows what I'm talking about.
jmsron@ron.rutgers.edu (Ron Natalie) (12/03/88)
The ARK LDM's are not usuable over normal telephone lines. They are limitted distance modems. You use them if you want to run a terminal over a largish amount of telephone-type wire beyond the normal RS-232 limits. You essentially connect four wires from the screws on one unit to the screws on the other. If you bought this thinking that you could use it on your telephone line, you are out of luck. -Ron
syd@dsinc.UUCP (Syd Weinstein) (12/05/88)
In article <8157@megaron.arizona.edu> jms@mis.arizona.edu (Joel Snyder) writes: >In article <8811301805050FA.GUWI@RAI.CC.FSU.EDU> James@FSU.BITNET (James Messer) writes: >asks about the ARK LDM-4. > >PS: I know that an LADA circuit is a 3004, or 2 of the 3002. But is >there a common nomenclature for LATA circuits? It usually takes >3 to 4 people before I can find one who knows what I'm talking about. A LATA or local access transport arrangement line, a bare piece of copper is measured in length in distance from one end to the co and then distance from the other end to the CO. It is then charged by the sum of those two distances. It is only really useful within the same CO. I had one for several years, and you have to be very careful. The speed drops off greatly as the distance goes up. At one mile you can do 19200, at our length, 3-4 miles it was more line 9600 only. The line is called a 9004 is our area, is a special beasty, and not many of the people know about them. It was not cheap, ran about 90/month when we dropped it over a year ago, up from the 24/month when we started it three years before that. Major complaint, until they invented a way to put sealing current on it (most 9004's are really dry, no sealing current even), it would fail once a month, or when it rained heavly. Also, without battery, every so often someone would swipe the pair for some other use. (Even though the connectors had rubber covers that were marked DATA. After the engineering change, all went well. We dropped due to change in office locations. -- ===================================================================== Sydney S. Weinstein, CDP, CCP Elm Coordinator Datacomp Systems, Inc. Voice: (215) 947-9900 {allegra,bellcore,bpa,vu-vlsi}!dsinc!syd FAX: (215) 938-0235
ron@ron.rutgers.edu (Ron Natalie) (12/07/88)
> PS: I know that an LADA circuit is a 3004, or 2 of the 3002. But is > there a common nomenclature for LATA circuits? It usually takes > 3 to 4 people before I can find one who knows what I'm talking about. 3002's are not metalic circuits. The LDM's won't work on them. You need a modem designed for telephone circuits. We like the Penril 9600FT for those. -Ron
qeds@mtuxo.att.com (01226-E.SCHULZ) (12/08/88)
If you have a non-loaded metallic 4-wire Local Area Data Channel
(LADC), why use a modem? Send your data digitally end-to-end.
Our group developed the AT&T 2500/2600 Data Service Units for
DDS, and these things can be used on LADC channels. Mean time
between DSU failures is around 17 years. This is the maximum
cable length (in miles) for various speeds and wire gauges:
Wire Gauge (AWG)
DSU Speed 19 22 24 26
__________________________________
9.6 Kbps 15.2 9.7 7.3 5.6
19.2 Kbps 10.7 6.6 5.0 3.9
56 Kbps 9.2 5.4 3.8 2.8
64 Kbps 9.2 5.4 3.8 2.8
Call me for more technical info. 1-800-247-1212 should get you to
a sales rep.
--
Ed Schulz, AT&T, Middletown, NJ
(201)957-3899 mtdcb!edsdyer@spdcc.COM (Steve Dyer) (12/09/88)
In article <3633@mtuxo.att.com> qeds@mtuxo.att.com (01226-E.SCHULZ) writes: >If you have a non-loaded metallic 4-wire Local Area Data Channel >(LADC), why use a modem? Send your data digitally end-to-end. >Our group developed the AT&T 2500/2600 Data Service Units for >DDS, and these things can be used on LADC channels. Mean time >between DSU failures is around 17 years. Can these be used legally on a LADS TelCo (I assume NeTel nomenclature for the same as LADC) circuit which runs from premise--CO--premise? I'm using a pair of 19.2kb Gandalf LDS309A data sets which do the job nicely, but a faster data rate would be great, assuming I can get appropriate synchronous serial interfaces which will do the job. Also, what is the cost of the 2500DSU? I'm sure many of us would be interested to know. -- Steve Dyer dyer@harvard.harvard.edu dyer@spdcc.COM aka {harvard,husc6,linus,ima,bbn,m2c,mipseast}!spdcc!dyer