nobody@cs.buffalo.edu (06/06/89)
How many devices can a single residential line support? At the moment I have 4
telephones, 1 answering machine, and 1 modem on the line. I am about to
add a second modem and another phone. Is this "safe", and will it work?
Thanx.
Davin.
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Davin Milun Internet: milun@cs.Buffalo.EDU
uucp: ..!{boulder,decvax,rutgers}!sunybcs!milun
BITNET: milun@sunybcs.BITNETjohn@ucbvax.berkeley.edu (John Higdon) (06/08/89)
In article <telecom-v09i0188m03@vector.dallas.tx.us>, nobody@cs.buffalo.edu writes: > How many devices can a single residential line support? At the moment I have > 4 telephones, 1 answering machine, and 1 modem on the line. I am about to > add a second modem and another phone. Is this "safe", and will it work? The limiting factor involved when adding devices to a telephone line is simply the number of ringers (or more precisely, ringer equivalence) on the line. When a device is "on hook", it presents no load to the line other than its ringer. If the device has no ringer (or its ringer equivalence is "0.0") it is totally invisible unless you take it off hook. If memory serves, I believe the maximum REN (Ringer Equivalence Number) allowed on a 1/1A ESS is 8. Higher than this, the CO will withhold ring current and you will never know anyone is calling you. This has actually happened to me and it was very embarassing when I turned in the trouble call. They told me I had too much stuff on the line. Add up all the RENs on your devices on any one line and if it's less than 8, you are probably OK. -- John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.uucp | San Jose, CA 95150 | M o o !
dave@rutgers.edu (Dave Levenson) (06/09/89)
In article <telecom-v09i0188m03@vector.dallas.tx.us>, nobody@cs.buffalo.edu writes: > How many devices can a single residential line support? At the moment I have > 4 telephones, 1 answering machine, and 1 modem on the line. I am about to > add a second modem and another phone. Is this "safe", and will it work? What you must do is add up the ringer equivalence numbers of the various devices you wish to connect. The maximum total REN for a given subscriber line depends upon the serving central office, and on the length of the loop. Your telco probably has the information, but it may be difficult to speak with the right person. Bellcore publication PUB61100 "Description of Analog Voiceband Interface Between the Bell System Local Exchange Lines and Terminal Equipment" is the definitive technical reference for this sort of thing. -- Dave Levenson Westmark, Inc. dave@westmark.uu.net Warren, NJ, USA {uunet | rutgers | att}!westmark!dave [The Man in the Mooney] N5848Q
len@csd4.milw.wisc.edu (Leonard P Levine) (06/10/89)
In article <telecom-v09i0191m03@vector.dallas.tx.us>, by decvax!decwrl!apple!zygot!john@ucbvax.berkeley.edu (John Higdon) writes: > If memory serves, I believe the maximum REN (Ringer Equivalence Number) > allowed on a 1/1A ESS is 8. Higher than this, the CO will withhold ring > current and you will never know anyone is calling you. Does this mean that I can surpress the ringing of my home phones when I want to just by increasing the number of equivalent ringers? If so, that would be very useful at times. + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + | Leonard P. Levine e-mail len@evax.milw.wisc.edu | | Professor, Computer Science Office (414) 229-5170 | | University of Wisconsin-Milwaukee Home (414) 962-4719 | | Milwaukee, WI 53201 U.S.A. Modem (414) 962-6228 | + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + [Moderator's Note: I think this would be an *awful* way to go about what you want to accomplish. It's like saying can I turn out the lights before I go to bed at night by short-circuiting the fuse box in the basement? Yes, of course you can. Why not regular off/on switches instead? PT]
d.m.p.@pro-party.cts.com (Don Peaslee) (06/11/89)
In article <telecom-v09i0188m03@vector.dallas.tx.us>, nobody@cs.buffalo.edu writes: > How many devices can a single residential line support? At the moment I have > 4 telephones, 1 answering machine, and 1 modem on the line. I am about to > add a second modem and another phone. Is this "safe", and will it work? I can give you an admittedly non-technical answer. I have 6 phones, 2 modems, and an answering machine all on one line and have no problem whatsoever. I'd bet that several more devices could be installed prior to my having any problems. You should be fine for the next couple of additions. Don
goldstein%delni.DEC@decwrl.dec.com (Fred R. Goldstein dtn226-7388) (06/12/89)
If I recall my Part 68 correctly, the rule on Ringer Equivalence
Numbers is that all devices must not have a combined REN greater
than 5. Not 6 or 8 as previously reported.
This is the standard that all CO switches are built to. Some may
actually support more, but the telco is obligated normally to allow
up to 5 REN total, and that's what they're now built for.
REN of 1 comes from the traditional electromechanical ringer, but
not even all of them are equal to 1. I have a Northern Telecom
deskset (1986 Link model) with a real bell (not a fire alarm chirper)
with an REN of 0.8A, which is typical of modern equipment. Some modems
and answering machines, which don't need to really ring, have RENs
in the 0.1 range.
A friend had trouble in her apartment, with phones not being audible,
and it turned out to be an REN violation. The answering machine
was something like 1.2, and there were four other phones... Unplugging
any one device made them all ring, but with the REN overload, the
ring voltage fell too low for them all to ring. SOme devices rang,
but were anemic, while others didn't ring at all. Yes, it's a violation
of telco rules to overload your line. If you really need to have more
bells, you should get an external bell relay.
fredcowan@marob.masa.com (John Cowan) (06/13/89)
In article <telecom-v09i0191m04@vector.dallas.tx.us> westmark!dave@rutgers.edu (Dave Levenson) writes: >In article <telecom-v09i0188m03@vector.dallas.tx.us>, nobody@cs.buffalo.edu >writes: >> How many devices can a single residential line support? At the moment I have >> 4 telephones, 1 answering machine, and 1 modem on the line. I am about to >> add a second modem and another phone. Is this "safe", and will it work? >What you must do is add up the ringer equivalence numbers of the various >devices you wish to connect. The maximum total REN for a given subscriber line The backward compatible maximum REN across the entire old-AT&T (BOC) system is supposed to be 5. So a maximum total REN of 5 should work on any private line anywhere, except perhaps one served by a Very Local Telco that hasn't upgraded since 1953. :-) But don't make assumptions: the local telco at my summer home, Taconic Telephone, is now one of the few all-digital telcos in the country! Fascist inews! Fascist inews! Fascist inews! Fascist inews! -- John Cowan <cowan@marob.masa.com> or <cowan@magpie.masa.com> UUCP mailers: ...!uunet!hombre!{marob,magpie}!cowan Fidonet (last resort): 1:107/711 Aiya elenion ancalima!
chip@vector.dallas.tx.us (Chip Rosenthal) (06/14/89)
goldstein%delni.DEC@decwrl.dec.com (Fred R. Goldstein dtn226-7388) writes: >X-TELECOM-Digest: volume 9, issue 196, message 5 of 6 >If I recall my Part 68 correctly, the rule on Ringer Equivalence >Numbers is that all devices must not have a combined REN greater than 5. Bingo! It's in subpart D. My Part 68 compilation says: "All registered terminal equipment and registered protective circuitry which can affect on-hook impedance shall be assigned a Ringer Equivalence. The sum of all such ringer equivalences on a given telephone line or loop shall not exceed 5 [...]" The rules and conditions for determining REN look pretty hairy. But you can say that about Part 68 in general. I remember way-back-when the story that the telco would sometimes check the impedance of the line through the house, calculate the ringer equivalence, and determine if you had illegal phones. I don't know if this was true, but just the same we had several phones with disconnected ringers in our house. (Omigosh. I hope the statute of limitations has run out :-) -- Chip Rosenthal / chip@vector.Dallas.TX.US / Dallas Semiconductor / 214-450-5337 "I wish you'd put that starvation box down and go to bed" - Albert Collins' Mom
pbreslin@alias.UUCP (Paul Breslin) (06/15/89)
If one has several old rotary dial phones and an old hand-me-down answering machine (all of untraceable origin) and an old 1200 baud modem (usually left powered off), how does one determine the REN number? Can I measure each device with an ohm meter or something? (I suspect many people have similar collections of junk plugged into their phone jacks.)
pbreslin@alias.uucp (Paul Breslin) (07/22/89)
If one has several old rotary dial phones and an old hand-me-down answering machine (all of untraceable origin) and an old 1200 baud modem (usually left powered off), how does one determine the REN number? Can I measure each device with an ohm meter or something? (I suspect many people have similar collections of junk plugged into their phone jacks.) [Moderator's Note: Without going to the trouble of measuring each one, I think you are safe in assuming one old phone equals one REN. Years ago we were told by telco don't put more than four extension phones on the line. The answering machine probably counts for a about half a REN. Three or four phones, an answering machine and a modem should get along okay. At home I have three extensions and a modem on one line; three extensions and and answering machine on the other line. PT]