GMS@PSUVM.BITNET (01/07/85)
Can anyone point me towards a modem that will work on a phone line
equipped with 'call-waiting'. The modems we have seen will lose
carrier when the call-waiting signals come through. This is wreaking
havoc for users of workstations who have this feature on their
phones. It should be possible to design a modem that will incorporate
a delay before dropping carrier. Is there such a beast?
Please send me email directly, or give me a call.
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Gerry Santoro
Microcomputer Information and Support Center GMS @ PSUVM (bitnet)
Penn State University !psuvax1!santoro (UUCP)
101 Computer Building santoro @ penn-state (CSNET)
University Park, PA 16802
(814) 863-4356jhh@ihldt.UUCP (John Haller) (01/08/85)
It's not the modem that needs changing, but the computer and terminal/workstation software that needs changing. Call waiting will interrupt the carrier for 2 seconds. If the DTEs will maintain DTR when DCD drops for a period of two seconds or less, most modems will maintain the connection. though with a two second noise burst. It would be even nicer if the terminal or computer notified you that there was a Call Waiting interruption, so that the operator could decide whether they wanted to answer this particular call. John Haller
dave@lsuc.UUCP (David Sherman) (01/08/85)
In article <1362GMS@PSUVM> GMS@PSUVM.BITNET writes: ||Can anyone point me towards a modem that will work on a phone line ||equipped with 'call-waiting'. This came up on the net some time ago. I've never heard of a modem which survives call-waiting, but apparently if you have call-forwarding as well you can call-forward the second half of your line to itself, and busy out the line to prevent the call-waiting signal from being received. Dave Sherman Toronto -- {utzoo pesnta nrcaero utcs}!lsuc!dave {allegra decvax ihnp4 linus}!utcsrgv!lsuc!dave
dwl@hou4b.UUCP (D Levenson) (01/09/85)
Q: Is there a modem compatible with call-waiting? A: Many modems have an option (strapped, dip-switched, or software-configured) known as "disconnect on loss of carrier". This is usually enabled by the factory-supplied defaults. If you disable this option *at both ends* then the modem will not break the line connection when the carrier is interrupted by call-waiting. However, if the modem momentarily loses carrier, it may receive one or more garbage characters when a call-waiting tone is applied. Also, your host computer's operating system may force the modem to disconnect by dropping its DTR (data terminal ready) signal when it senses the modem's dropping carrier detect. Finally, it is desireable that the host treat loss of carrier as a disconnect and logoff request from the user. Overriding this feature, while providing some imunity to call-waiting, may leave a port logged in after a user has hung up without logging off. Another user who dials in shortly thereafter will find him/herself already logged in as the previous user. Definitely a security-hole. -Dave Levenson AT&T-ISL, Holmdel
cmoore@amdimage.UUCP (chris moore) (01/10/85)
> ... If the DTEs will maintain DTR when DCD drops for a period of > two seconds or less, most modems will maintain the connection. > John Haller Actually, the definition of a carrier loss us usually a loss of carrier for 1 second +/- 0.1 sec. This means that most modems will disconnect after one second of carrier loss, and a call waiting beep is usually longer than that. -- "You can't get out backwards, you have to go forwards to go back" Chris Moore (408) 749-4692 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!amdimage!cmoore ARPA: amdcad!amdimage!cmoore@decwrl.ARPA
ron@brl-tgr.ARPA (Ron Natalie <ron>) (01/10/85)
> Can anyone point me towards a modem that will work on a phone line > equipped with 'call-waiting'. The modems we have seen will lose > carrier when the call-waiting signals come through. This is wreaking > havoc for users of workstations who have this feature on their > phones. It should be possible to design a modem that will incorporate > a delay before dropping carrier. Is there such a beast? > > Please send me email directly, or give me a call. > The modification has to be done on both ends. I saw a software fix for this on UNIX, but it's pretty disgusting. If you have call forwarding on the same line, you can just forward the calls somewhere else so you don't get the beep click while using the modem. -Ron
gnu@sun.uucp (John Gilmore) (01/13/85)
> Q: Is there a modem compatible with call-waiting?
It's really funny to see all the people from AT&T replying to this.
Why didn't you guys design the "feature" so it could be turned off?
E.g. dialing *nn (nn=two unused digits) would disable call waiting for
this call and give you a dial tone. Then we could set up autodial
modems to do this (or do it manually), while not affecting voice calls.
Lack of consideration of modem users in home settings has been
the hallmark of AT&T phone "features".
One of the rocks upon which the nonprofit Usenetlike PCNet project
foundered was that it took a separate phone line -- we could not figure
a reasonable way to attach an auto-answer computer to a voice phone line
without destroying its usefulness as a voice line. Likely the channel
used for this kind of communication will be video cable -- the phone
pholks missed the window.
Q: Is there a phone network compatible with modems?dwight@timeb.UUCP (Dwight Ernest) (01/13/85)
> > ... If the DTEs will maintain DTR when DCD drops for a period of > > two seconds or less, most modems will maintain the connection. > > John Haller > > Actually, the definition of a carrier loss us usually a loss of > carrier for 1 second +/- 0.1 sec. This means that most modems > will disconnect after one second of carrier loss, and a call waiting > beep is usually longer than that. > Chris Moore Once again, however, this point up the fact that some modems don't act that way, but leave it up to the communications software. For instance, I use a Hayes Smartmodem-1200 with my Compaq portable P.C. under PCDOS 2.1; the comm s/w is YAM (Yet Another Modem) by Chuck Forsberg at Omen Technology, and I like it very much, partially because it permits me to define the amount of time that passes before a loss of carrier is interpreted as a loss of connection, in the range of about 0.05 seconds to about 15 seconds. (BTW, if anyone would like further info about YAM, let me know via mail.) -- --Dwight Ernest KA2CNN \ Usenet:...vax135!timeinc!dwight Time Inc. Editorial Technology Group, New York City Voice: (212) 554-5061 \ Compuserve: 70210,523 Telemail: DERNEST/TIMECOMDIV/TIMEINC \ MCI: DERNEST "The opinions expressed above are those of the writer and do not necessarily reflect the opinions of Time Incorporated or its management." "Doctor, we can't go flitting about the Universe with a dormant Gravis lying about the console, now can we?" --Tegan -----------------------------------------------------------------------------
dwight@timeb.UUCP (Dwight Ernest) (01/14/85)
> > Q: Is there a modem compatible with call-waiting? > > It's really funny to see all the people from AT&T replying to this. > Why didn't you guys design the "feature" so it could be turned off? Awwww, come on, give those AT&T people a break! Weren't you ever in a social setting (a party, perhaps), and someone asks you what you do for a living, and you answer you're "in computers," and then they start asking all kinds of questions about their Commodore 64 or some such nonsense, and end up blaming you for their problems with the machine? That's roughly analogous to what you're doing when you "blame" the AT&T people who took the trouble to make a thoughtful reply to the call waiting question. Unlike Sun, AT&T is a rather large company, and the chances are EXTREMELY remote that these AT&T people had ANYTHING to do with the design or the implementation of Call Waiting and the other Custom Callling stuff. They probably agree with your criticism of it, in fact. So please don't flame 'em! In fact, I was at a party the other day and got "blamed" for something that was published in TIME, and I have nothing more than to do with what gets published therein than you do. -- --Dwight Ernest KA2CNN \ Usenet:...vax135!timeinc!dwight Time Inc. Editorial Technology Group, New York City Voice: (212) 554-5061 \ Compuserve: 70210,523 Telemail: DERNEST/TIMECOMDIV/TIMEINC \ MCI: DERNEST "The opinions expressed above are those of the writer and do not necessarily reflect the opinions of Time Incorporated or its management." "Doctor, we can't go flitting about the Universe with a dormant Gravis lying about the console, now can we?" --Tegan -----------------------------------------------------------------------------
richard@islenet.UUCP (Richard Foulk) (01/15/85)
> Can anyone point me towards a modem that will work on a phone line > equipped with 'call-waiting'. The modems we have seen will lose > carrier when the call-waiting signals come through. This is wreaking > havoc for users of workstations who have this feature on their > phones. It should be possible to design a modem that will incorporate > a delay before dropping carrier. Is there such a beast? > > Please send me email directly, or give me a call. Yes. As one example; if you use Hayes modems at both ends and you set them up with a command like: AT S10=30 then both ends should wait 3 seconds before hanging up, which would probably be sufficient. The default setting on the Hayes is 7 or 7-tenths of a second. I haven't tried this stuff but it seems like it should work okay.
nessus@nsc.UUCP (Kchula-Rrit) (01/17/85)
> > Q: Is there a modem compatible with call-waiting? > > It's really funny to see all the people from AT&T replying to this. *** REPLACE THIS LINE WITH YOUR MESSAGE *** Check-out people frequently gripe to me about their cash registers when they find out that my company made them(in another division, thank goodness!) Kchula-Rrit
rjk@mgweed.UUCP (Randy King) (01/17/85)
As John pointed out, it is indeed the carrier interruption that causes a drop in the signal. With the new AT&T 4000 autodial 300/1200 baud modem, there is a data loss timer that is programmable by you to avoid data drop during call waiting interrupts. The modem is programmable via menu on your terminal or through escape sequences. It has a built in speaker and tons of other features. For more info, I have been told to refer you to AT&T Information Systems offices, but if you don't get the info you want, then contact me directly via this network and I'll get you the info. By the way, any of you ATTIS folks out there care to publish a number to handle these queries? It sure would help out a lot! Randy King AT&T-CP@MG ihnp4!mgweed!rjk
rjk@mgweed.UUCP (Randy King) (01/17/85)
Dave makes a good point about the security hole where he describes the modems that either ignore loss of carrier or immediately act on it. The AT&T 4000 modem is timer-programmable so that you can tell it *how long* to ignore the loss of carrier. This lessens the security hole and gives you call waiting immunity. Randy King AT&T-CP@MG ihnp4!mgweed!rjk