steele@ee.ecn.purdue.edu (Richard Steele) (12/08/89)
Here at Purdue U., we now have access to something called data over voice (DOV) units. These are small boxes, about the size of a regular modem, that gives the user a 9600 bps asynchronous data line to the University computer. Not only is the bugger faster than a modem, _but it leaves the phone free for regular use_. We can still receive and make calls with the DOV working with no obvious distortion on the line. Thus, in addition to having a reasonably fast connection (and I used to think a 2400 baud modem was speedy!), I don't have to take the wrath of my roomates for hogging the phone line all night long. The DOV unit connects to the phone line before any other equipment; i.e. there's are line in and line out jacks. In addition, just like a Hayes Smartmodem, there are a plethora of LEDs on the front like CD (carrier detect), RD (receive data), SD (send data), etc. Question: How would something like this work? The phone company _does_ need to make some changes on their end, but the phone line remains the same. So, what magic is involved here? Thanks to all who respond... Richard A. Steele Purdue University
Steve Elias <eli@spdcc.com> (12/11/89)
Richard Steele <steele@en.ecn.purdue.edu> writes: >Here at Purdue U., we now have access to something called data over >voice (DOV) units. These are small boxes, about the size of a regular >modem, that gives the user a 9600 bps asynchronous data line to the >University computer. Not only is the bugger faster than a modem, _but >it leaves the phone free for regular use_. >So, what magic is involved here? Thanks to all who respond... Try screaming into the phone while you are watching 960 cps output on your CRT... does the data rate slow? I think there are some nifty boxes out there which will encode the voice digitally and use any excess digital bandwidth for other data. Maybe this is the sort of device Purdue has given you. Now for the next step, you must TAKE IT APART, of course! The sign of a truly curious engineer. what are the labels On the outside of the box and on internal boards ? Steve Elias ; eli@spdcc.com ; 6179325598 ; 5086717556 ; { *disclaimer(); }
Miguel_Cruz@um.cc.umich.edu (12/11/89)
A little while ago, Richard Steele wrote: >Here at Purdue U., we now have access to something called data over >voice (DOV) units. These are small boxes, about the size of a regular >modem, that gives the user a 9600 bps asynchronous data line to the >University computer. Not only is the bugger faster than a modem, _but >it leaves the phone free for regular use_. In response to which Steve Elias wrote: > I think there are some nifty boxes out there which will encode the > voice digitally and use any excess digital bandwidth for other data. > Maybe this is the sort of device Purdue has given you. Actually, I'd think it much more likely that there are just extra pairs running from all the university phone jacks that are activated on request and connected to the "University computer". Here at the University of Michigan (which I tend to assume works exactly the same as everyplace else), they will supply dorm residents with line drivers for a hundred bucks a year. Sometimes they refer to them as "data over voice" or other similarly deceptive hi-tech terms, but there's nothing magical about it. They work at 19200 baud and connect through Secondary Communications Processors (whatever they are) located in various campus buildings. I don't even think they're switched by the campus PBX...just wired straight.
lars@salt.acc.com (Lars J Poulsen) (12/12/89)
A little while ago, Richard Steele wrote: > >Here at Purdue U., we now have access to something called data over > >voice (DOV) units. These are small boxes, about the size of a regular > >modem, that gives the user a 9600 bps asynchronous data line to the > >University computer. Not only is the bugger faster than a modem, _but > >it leaves the phone free for regular use_. In response to which Steve Elias speculated that these boxes might be delivering unused bandwidth of a digital subscriber loop for data use. In article <2022@accuvax.nwu.edu> Miguel_Cruz@um.cc.umich.edu writes: >Actually, I'd think it much more likely that there are just extra >pairs running from all the university phone jacks that are activated >on request and connected to the "University computer". >They work at 19200 baud and connect through Secondary Communications >Processors (whatever they are) located in various campus buildings. I >don't even think they're switched by the campus PBX...just wired >straight. The data communication magazines carry ads from several manufacturers of Data Over Voice units. They are carrier-frequency devices that share the local loop to provide a permanent modem circuit on the subscriber pair while allowing normal use of the telephone. The data signal is recovered by a "modem" box (twin to the one on the subscriber end) where the line enters the PBX. I recently learned that our local GTE outfit offers DOV on residential lines. The DOV circuit goes into a CBX (data PBX for asynch traffic) and is delivered to other DOV lines or to dedicated business data liens on the other side. (I wish they had an X.25 option on the other side). Several of the high-tech companies in town have access lines to this switch, as does the university (UCSB). The DOV facility provides 19.200 bps service for about the same cost per month as an extra residential subscriber loop. Unfortunately, my employer is unlikely to replace the current 5 dial-in lines with connections to this service. / Lars Poulsen <lars@salt.acc.com> (800) 222-7308 or (805) 963-9431 ext 358 ACC Customer Service Affiliation stated for identification only My employer probably would not agree if he knew what I said !!
segal%cell.mot.COM@uunet.uu.net (Gary Segal) (12/12/89)
steele@ee.ecn.purdue.edu (Richard Steele) writes: >Here at Purdue U., we now have access to something called data over >voice (DOV) units. These are small boxes, about the size of a regular >modem, that gives the user a 9600 bps asynchronous data line to the >University computer. Not only is the bugger faster than a modem, _but >it leaves the phone free for regular use_. We can still receive and >make calls with the DOV working with no obvious distortion on the >line. Thus, in addition to having a reasonably fast connection (and I >used to think a 2400 baud modem was speedy!), I don't have to take the >wrath of my roomates for hogging the phone line all night long. >The DOV unit connects to the phone line before any other equipment; >i.e. there's are line in and line out jacks. In addition, just like a >Hayes Smartmodem, there are a plethora of LEDs on the front like CD >(carrier detect), RD (receive data), SD (send data), etc. >Question: How would something like this work? The phone company >_does_ need to make some changes on their end, but the phone line >remains the same. >So, what magic is involved here? Thanks to all who respond... Carnegie-Mellon University has had something called "Metropolitan Campus Network" (MCN) for a while (since fall 1986, I think). It gives people on certain CO's a 9600bps data link to the campus computing network. It is implemented using Gandolf DOV modems (model number escapes me), which sounds very much like the beast Purdue is using. When installed, the connection looks like this: +-----------+ | 2-wire to CO | +-----------+ =======| DOV Modem |=======================| DOV Modem |========= 2-wire | | | | | in a Bank |Many Pairs to VF | | | | | O' DOVs |to CO equip. +-----------+ | | +-----------+equip. (phones, ! | | ! modems, ! | | ! faxes...) ! | | ! ! | | Many RS-232 links to RS-232 to computer | | data switches & | | terminal concentrators | | Customer Premise | Poles, etc... | Central Office VF = Voice Frequancy How does it work? Simple, if the line between the CO and the customer premise is pretty good, you can get more than 300-3400Hz bandwidth out of it. The DOV modems use carrier frequancies above 3400Hz. They have a filter that sits between the DATA/Voice side and the VF side that removes the data signals. In addition, all of the normal telephone signals are passed through without changes. At the CO end, the data is "peeled" off before the channel banks or other such CO equipemnt. Thus, the DOVs are transparent to VF and telephone signaling. In order for this to work, the pair from the CO to your premise must be pretty darn good. When MCN was first offered by Bell of PA and CMU, they listed the exchanges that you could get it on. I believe they had installed DOV shelves in three CO's, so if you were attached to any of those, you could get it. In addition, they stated that if you were more than a certain distance from the CO (2 or 3 miles, I think), it wouldn't work. There was also talk of making a 64Kbs link availible, however I don't know if it was going to be by DOV or ISDN. Oh yeah, it was fairly expensive for your average student, something like $100 to install, $200 for the DOV and $25 a month. Maybe somebody at CMU can bring us up to date on the current state of MCN. Gary Segal, Motorola C.I.D. 1501 W. Shure Drive ...!uunet!motcid!segal Arlington Heights, IL 60004 Disclaimer: The above is all my fault. +1 708 632-2354
scp@bpa.bell-atl.com (Steve Parowski) (12/12/89)
In article <1978@accuvax.nwu.edu> Richard Steele <steele@en.ecn.purdue.edu> writes: >X-Telecom-Digest: Volume 9, Issue 561, message 5 of 5 >Here at Purdue U., we now have access to something called data over >voice (DOV) units. These are small boxes, about the size of a regular >modem, that gives the user a 9600 bps asynchronous data line to the >University computer. Not only is the bugger faster than a modem, _but >it leaves the phone free for regular use_. We can still receive and >make calls with the DOV working with no obvious distortion on the line. >Question: How would something like this work? The phone company >_does_ need to make some changes on their end, but the phone line >remains the same. >So, what magic is involved here? Thanks to all who respond... Here in Bell Atlantic we offer this as a tarriffed service it is called LANgate or Central Office Local Area Network. See your local sales rep for prices. How it works...... That box that has jacks for your phone and your terminal converts your terminal signal from digital to analog. The box then Frequency multiplexes your voice and the analog data onto the same copper pair. At the Purdue Central Office this process is reversed. This is an excellent way to provide 9600 bps without wiring changes or expensive modems. Steve Parowski Wal La
Michael.Fryd@g.gp.cs.cmu.edu (12/13/89)
Around here, DOV means "Data Over Voice" and refers to the Gandlaf DOV 640 modems that provide 64kb synchronous communications over a standard voice pair, without interfering with normal voice service. In Pittsburgh, this service is known as Metropolitan Campus Network (MCN) and is provided by some combination of Carnegie-Mellon University (CMU) and Bell of PA. My house was a beta-test site for this service a few years ago, and in the many technician visits I picked up a few things. I have since moved, so some of the details may have changed. Two DOV modems are actually used for each house served. One is placed at the Bell of PA Central office(CO), between the switch and the cable pair to your house. The second DOV is installed in your house, electrically between the Network Interface Jack and your existing household phone wires. +---------+ | Central | voice +--------+ data and voice +---------+ voice +---------+ | Office |-------| CO DOV | ----------------| user DOV|-------|telephone| | switch | +--------+ +---------+ +---------+ +---------+ | | |data |data Port Selector in CO--- + +-------Home terminal or PC The modems communicate using frequencies above the voice band. The DOVs completely ignore all of the normal telephone signals, allowing uninterrupted data communications regardless of whether the phone line is in-use, ringing, or idle. The DOV operates as 64Kb synchronous. In order for the DOVs to work you must be within a pre-set distance (I think on the order of a few miles) from the CO. The real problem with this setup, is that it only allows you to communicate with the CO. Bell of PA installed port selectors in three of the COs near CMU. These were connected by fiber to CMU. At my house, I just plugged my terminal into the DOV, and hit return. This got the attention of Bell's port selector. There were few destinations at CMU that I could select (Most of which were additional port selectors or terminal concentrators). When I left the program, only 9600 and 19.2 kBd async was supported, with plans for 64Kb, possibly using Serial Line IP. The most amazing thing was that the system worked very well. Voice and data operated independently on the same copper pair. Incoming and outgoing calls did not affect data at all. I have no idea what the applicable tariffs were. Payments were made to CMU, but installations and service was provided by Bell of PA. I was always amazed that the Bell service operators (just dial 611) were able to cope with MCN trouble reports. The biggest problem during the testing phase was noise on the phone line. The DOVs went through quite a few revisions before there was no audible interference with the standard voice usage. If I've left anything out, let me know and I'll be happy to give the answer if I know it. Michael Fryd President Voice: (412) 751-5557 MEFCO, Inc. Fax: (412) 751-8403 2401 Coulter Road Email: Michael.Fryd@CS.CMU.EDU McKeesport, PA 15131-4251
ggray@uunet.uu.net (George Gray) (12/13/89)
DOV (Data Over Voice) is a techniqiue that uses a single pair of wires that permits both data and voice on a line simultaneously. The data portion of the service is modulated at a higher frequency outsied of the normal voice conversation. For example, the voice conversation is at 300-4000 Hz (approx) and the data would be sent at 40Khz on the receive side and 80Khz on the transmit side. Because of the frequencies involved, the operating distances between 2 DOV units is usually less than 10,000 feet. DOV units are connected similar to a modem with a TESLSET jack and a TELCO LINE jack plus power. There are several maufacturers of these units among them are TELTONE and APPLIED SPECTRUM TECHNOLOGIES. George Gray
@sun.acs.udel.edu:sjm@sun.acs.udel.edu (sjm) (12/14/89)
Here in Delaware I have been told that it costs $100 to install a DOV line and $25/month afterwords. We are installing a campus wide fiber optic backbone so in a year or so most of the DOV lines will go away. Eventually the Centrex system will too. (Oh goody, then we have to learn a new phone system again.) Steven Morris
steele@ee.ecn.purdue.edu (Richard Steele) (12/15/89)
Thanks to everyone who replied (both by mail and news) to my query about "data over voice" (DOV) units. I'd like to reply to everyone who responded, but since it's finals week here (I'm sure everyone remembers those), I'll save time by responding to [Michael.Fryd@g.gp.cs.cmu.edu] since his experience with DOV is very close to mine: >Around here, DOV means "Data Over Voice" and refers to the Gandlaf DOV >640 modems that provide 64kb synchronous communications over a >standard voice pair, without interfering with normal voice service. This is exactly the unit we have here. >In Pittsburgh, this service is known as Metropolitan Campus Network >(MCN) and is provided by some combination of Carnegie-Mellon >University (CMU) and Bell of PA. This is similar to the arrangement Purdue has... >Two DOV modems are actually used for each house served. One is placed >at the Bell of PA Central office(CO), between the switch and the cable >pair to your house. The second DOV is installed in your house, >electrically between the Network Interface Jack and your existing >household phone wires. >+---------+ >| Central | voice +--------+ data and voice +---------+ voice +---------+ >| Office |-------| CO DOV | ----------------| user DOV|-------|telephone| >| switch | +--------+ +---------+ +---------+ >+---------+ | | > |data |data >Port Selector in CO--- + +-------Home terminal or PC >The modems communicate using frequencies above the voice band. The >DOVs completely ignore all of the normal telephone signals, allowing >uninterrupted data communications regardless of whether the phone line >is in-use, ringing, or idle. The DOV operates as 64Kb synchronous. >In order for the DOVs to work you must be within a pre-set distance (I >think on the order of a few miles) from the CO. I believe this was the general concensus of the many replies I've gotten. Perhaps my biggest problem was that I didn't realize the simple twisted pair could handle such large bandwidths. Why is there a limit on the distance to the CO? Is there any reasonable way to increase this? >The real problem with this setup, is that it only allows you to communicate >with the CO. Bell of PA installed port selectors in three of the COs >near CMU. These were connected by fiber to CMU. [more info deleted] This is where the Purdue system differes (slightly) from the one at CMU. Since Purdue effectively owns the local network (i.e. we have to dial "9" to get an off-campus number), the "CO" is actually on-campus, very near the computer setups. Our hookup is to an ISN (Integrated Services Network), which is, I believe, a product from AT&T. We can go from there directly to most campus networks or go to the SDS (Serial Data Switch) to get to others, including those off campus. (I could, if I had the desire and the account, log onto a computer at Indiana University from the comfort of my own home! Life _is_ wonderful...) >When I left the program, only 9600 and 19.2 kBd async was supported, >with plans for 64Kb, possibly using Serial Line IP. Unfortunately, ISN (I think as Purdue has it configured) only supports 9600 baud. Unless I'm doing a _big_ file transfer to my home PC, this is very acceptable. Of course, there's the old programming adage that a project will fill the time alotted; a loose corollary would be a user always fills the bandwidth provided... :-) :-) >The most amazing thing was that the system worked very well. Voice >and data operated independently on the same copper pair. Incoming and >outgoing calls did not affect data at all. I definately agree. The system is _much_ slicker than using a 2400 baud dialup. Not only is it faster, but my roomates are much happier now that they have a phone again. >I have no idea what the applicable tariffs were. Payments were made >to CMU, but installations and service was provided by Bell of PA. I >was always amazed that the Bell service operators (just dial 611) were >able to cope with MCN trouble reports. We make our payments to our residence hall; the program right now is limited to most of the housing units, with plans to expand to off-campus users. I'm not sure how this would affect the CO connections, since Purdue has its own CO -- I hate to think of the mess it might cause! My roomate (_he's_ the expert in telephony) insits we should just go to ISDN; I'll bring him back to this century sometime before lunch. :-) As for cost, we pay $100 for the academic year, which includes charges from the CO. The unit is rented and there is no monthly fee. From several responses I've gotten, I'd say this is a competetive deal... >Michael Fryd >President Voice: (412) 751-5557 >MEFCO, Inc. Fax: (412) 751-8403 >2401 Coulter Road Email: Michael.Fryd@CS.CMU.EDU >McKeesport, PA 15131-4251 Thanks for the helpful response... Richard A. Steele Purdue University