atn@cory.berkeley.edu (Alan Nishioka) (02/13/91)
Thank you to all who answered my previous message about my project causing the phone to stop ringing. I responded via EMAIL. However, in response to my article, John Higdon brought up a problem that had been bothering me. He said that my project SHOULD comply with the various parts of the FCC rules since it needed to connect directly to the phone network. Now, many books and magazines regularly publish projects that connect to the phone line. Even the usually respectable TELECOM Digest recently published several such projects. I don't think any of them have been certified anything by anyone. I see two issues involved: One of safety (to craftspersons, etc. ) and the other of just following the rules. I can see if I were going to sell these devices that I would be interested in both, but as a hobbyist I am mostly interested in the first. I understand there are network interface devices that one can buy and thus have any device automatically safe and certified to connect to a line, but these are out of my budget. I also don't see how they make that much of a difference. I plan to power my project using a 12VDC transformer unit since the lights take more current than the line can provide. I have a 1MEG/5MEG voltage divider across the line to read voltages and plan to drop a 255ohm resistor across the line with a transistor for a hold function. All of this is prefaced by a bridge rectifier. Is this safe? Are there other concerns here that I am missing? Should *anyone* build *anything* that connects to the phone line? Can it be reasonably priced? Does the phone company really care? Should I do it anyway and just kinda feel guilty? :-) Alan Nishioka KC6KHV atn@cory.berkeley.edu ...!ucbvax!cory!atn 974 Tulare Avenue, Albany CA 94707-2540 37'52N/122'15W +1 415 526 1818
jon_sree@world.std.com (Jon Sreekanth) (02/16/91)
In article <74667@bu.edu.bu.edu> atn@cory.berkeley.edu (Alan Nishioka) writes: > Is this safe? Are there other concerns here that I am missing? The thrust of FCC 68 is that you don't damage or overload the telephone network. Hence the load limitations : maximum of 1.6K AC to ring current, max of 5 Meg DC on-hook. Another concern is signal power injected back to tip and ring. If your device does not intend to send back audio signals, then there are (generous) limits on out of band signal power, such as leakage from high frequency clocks in your digital section. The isolation requirements call for up to 1500V of insulation between tip/ring and any user accessible, outside parts of your box. FCC 68 also specifies that after a simulated lightning strike, 800V spike, 10uS rise, 560uS fall, 25 amp max surge, your equipment should still meet the impedance and signal power limitations. If you use an MOV on tip and ring, that should cover it. A relatively new requirement, UL 1459, is required from July, 1991 onwards (for phones, I'm told). The big deal about this test is your circuit must not burst into flames upon application of 600V RMS across tip and ring for 30 minutes or more. (The test is sneaky: if you use a series fuse, they're allowed to current limit just below the fuse limit, and see if the rest of your circuit burns) All this sounds a little overwhelming, I know, but the reason it's so fresh in my memory is because we're going through the process ourselves. I covered the main points above, but there might be some more that I missed. > Should *anyone* build *anything* that connects to the phone line? Can > it be reasonably priced? Does the phone company really care? Should > I do it anyway and just kinda feel guilty? :-) From personal experience, if an experimental circuit is briefly connected across a line, the telephone company does not notice it. But I'd not leave such a circuit connected while I'm not around to observe it. My judgement is : the few dollars saved by leaving a hacked up circuit connected to the line are not worth the potential risk of the insurance company refusing to pay for a fire or personal injury that the device caused (to take an extreme example). Regards, Jon Sreekanth Assabet Valley Microsystems Fax and PC products 346 Lincoln St #722, Marlboro, MA 01752 508-562-0722 jon_sree@world.std.com
berger@iboga (Mike Berger) (02/16/91)
atn@cory.berkeley.edu (Alan Nishioka) writes: > Now, many books and magazines regularly publish projects that connect > to the phone line. Even the usually respectable TELECOM Digest > recently published several such projects. I don't think any of them > have been certified anything by anyone. The books that I've seen generally include a caveat that the projects don't necessarily meet legal interface or registration requirements. > I see two issues involved: One of safety (to craftspersons, etc. ) and > the other of just following the rules. I can see if I were going to > sell these devices that I would be interested in both, but as a > hobbyist I am mostly interested in the first. > Is this safe? Are there other concerns here that I am missing? > Should *anyone* build *anything* that connects to the phone line? Can > it be reasonably priced? Does the phone company really care? Should > I do it anyway and just kinda feel guilty? :-) The phone company is interested in protecting their employees and equipment. Unregistered devices can potentially disrupt somebody elses' service or put dangerous voltages on the phone line. If you DO coincidentally cause problems, it's a good bet that the phone company will disconnect your service without notification and you may have a very hard time getting it restored. I suspect that the authors of the articles you mentioned would point out that you could connect the devices to your OWN local telephone switch without worrying about tariffs or registration. Mike Berger Department of Statistics, University of Illinois AT&TNET: 217-244-6067 Internet: berger@atropa.stat.uiuc.edu
sichermn@beach.csulb.edu (Jeff Sicherman) (02/16/91)
This may be a dumb question but ... Is there any device that one could insert in place of or on the customer side of the Network Interface that would serve the functions for protecting the phone company equipment and employees from any real or imagined damage from faulty project design or construction ? Would such device prevent the CO from detecting the attached equip- ment and would it meet the FCC regulatory requirements ? Jeff Sicherman
julian%bongo.UUCP@nosc.mil (Julian Macassey) (02/16/91)
In article <74667@bu.edu.bu.edu> atn@cory.berkeley.edu (Alan Nishioka) writes: X-Telecom-Digest: Volume 11, Issue 114, Message 4 of 10 > However, in response to my article, John Higdon brought up a problem > that had been bothering me. He said that my project SHOULD comply > with the various parts of the FCC rules since it needed to connect > directly to the phone network. Stuff deleted > I see two issues involved: One of safety (to craftspersons, etc. ) and > the other of just following the rules. I can see if I were going to > sell these devices that I would be interested in both, but as a > hobbyist I am mostly interested in the first. This comes up every now and again. Yes, if you interpret the rules as a paper pusher, you can't attach anything to the line that isn't certified as meeting FCC Part 68. But then how would you design and test a device in order to take a "production model" of it to take to an FCC lab for testing? This is obviously silly and not the intent of the regs. So yes, although it is by the book illegal, you can make one of devices for your own use. The telephone police are unlikely to call. If you want to make it availble to the public as a product, get it FCC certified or the telephone police will pay a visit. Of course if a device violates some of the FCC rules, it may not work very well. The rules are there partly as a quality check. But you don't have to be worried about stuff like REN measuremnt if you have nothing attached when the phone is on hook etc. Now the "damage to the network" myth. If you attach anything strange to your phone line, the only part of the network liable to be put out of commission is your phone line. If you short the line you will busy it out. If you open the line, it will look like there is no phone attached. It is much, much more dangerous to mess with mains electricity, yet people do that all the time. Yes, if you really mess with electricity, the whole street can go dark. Yes, you can build your own electrical devices and connect them. Funny world isn't it? Please tinker with your phones and equipment. It is the best way to learn. It is hard to kill yourself playing with phones. It is hard to cause fires playing with phones. I wish I could say the same about mains electricity. Julian Macassey, n6are julian@bongo.info.com ucla-an!denwa!bongo!julian N6ARE@N6YN (Packet Radio) n6are.ampr.org [44.16.0.81] voice (213) 653-4495
carroll@ssc-vax.uucp (Jeff Carroll) (02/17/91)
In article <74667@bu.edu.bu.edu> atn@cory.berkeley.edu (Alan Nishioka) writes: > However, in response to my article, John Higdon brought up a problem > that had been bothering me. He said that my project SHOULD comply > with the various parts of the FCC rules since it needed to connect > directly to the phone network. He's right, legally speaking. The FCC is pretty specific about what you can connect to the PSTN, for a good reason - because in our deregulated telecom environment, they're the only ones who can be. > Now, many books and magazines regularly publish projects that connect > to the phone line. Even the usually respectable TELECOM Digest > recently published several such projects. I don't think any of them > have been certified anything by anyone. Most if not all of them are illegal. The more savvy publishers and kit-sellers (e.g., Radio Shack) will *tell* you not to connect these things to the PSTN - that they are just fine to connect to your in-house intercom, but shouldn't be connected to your phone wires. > I see two issues involved: One of safety (to craftspersons, etc. ) and > the other of just following the rules. I can see if I were going to > sell these devices that I would be interested in both, but as a > hobbyist I am mostly interested in the first. There's a third issue - protecting the integrity of the network. As a telephone subscriber, you consume an amount of network resources. In order to keep the cost of billing within the troposphere, telco doesn't go to the trouble of measuring many of the resources you use such as seconds of dial tone, number of unsuccessful calls, local office battery power consumed, etc. This does not mean that you are granted a license to use these resources wantonly, carelessly, or in such a way as to impair the quality of service delivered to other subscribers, or to make it unreasonably costly for telco to provide you service. In a circuit-switched network, it is pretty hard for one subscriber to impair another's service, unless it's by calling that subscriber repeatedly and continuously. (Assuming that everyone has private lines.) In other kinds of network, it's a lot easier; witness what broadcast storms or sendmail worms can do to a LAN or an Internet. In Europe (particularly in the Netherlands), the PTT has serious problems with pirate broadcasters setting up shop on the cable TV network. Now, I'm not trying to tell you that you can't attach your well-designed, well-built project to the PSTN; I'm just trying to explain to you why telco is justified in cutting you off or seeking legal remedies when your non-certified device causes chaos in the central office. > I understand there are network interface devices that one can buy and > thus have any device automatically safe and certified to connect to a > line, but these are out of my budget. I also don't see how they make > that much of a difference. They make a difference because they (at least to the engineers at the FCC) prevent you from degrading the network. Note to flamers: I'm not suggesting that telco has the Public Interest primarily or even significantly at heart. Nor am I suggesting that Judge Greene knows anything about technology. Nor am I suggesting that just because the FCC says something makes it so. I'm just pointing out that system engineering is what it is, and in order for a system to work, one needs to respect the designers' intentions. Jeff Carroll carroll@ssc-vax.boeing.com
macy@usenet.ins.cwru.edu (Macy Hallock) (02/23/91)
In article <telecom11.124.3@eecs.nwu.edu> Jeff Sicherman writes: > Is there any device that one could insert in place of or on the > customer side of the Network Interface that would serve the functions > for protecting the phone company equipment and employees from any real > or imagined damage from faulty project design or construction ? Sure! Somewhere in my basement I have a couple of KS-20721 Line Protection Devices. I can strap them up as STC's for you, too. Ohio Bell swore these were absolutely necessary to prevent the destruction of the network by non-Bell equipment ... seems like that was only a few years ago, as I recall. If these are not acceptable, I might be able to find some CDH or STP type units for you ... maybe we should hook them up in front of John Higdon's Panasonic PBX to keep it from degrading the network as we know it ... (Sorry for the sarcasm here, but it really wasn't that long ago that AT&T and the Bell Companies assured the FCC that couplers were absolutely mandatory to protect the network. And the Bells wonder why their "concerns" meet with so much skepticism these days!) Seriously, there used to be FCC approved units for this purpose around. I think they were used in answering machines extensively at one time. I recall seeing an ad for FCC registered line isolation modules for incorporation into equipment not too long ago. Macy M. Hallock, Jr. macy@fmsystm.UUCP macy@NCoast.ORG uunet!aablue!fmsystm!macy
jimmy@icjapan.info.com (Jim Gottlieb) (03/03/91)
John Higdon <john@zygot.ati.com> writes: > Macy Hallock <fmsys!macy@usenet.ins.cwru.edu> writes: >> Somewhere in my basement I have a couple of KS-20721s > A final note: to its credit, the CPUC eventually ordered Pac*Bell to > refund ALL money EVER paid by customers for "network protection" > devices. This included installation and montly charges plus interest. The really neat part of this was that they still took orders for these devices (we always called them "couplers") after they announced that anyone could get this refund for the asking. Knowing this, I ordered a ton of RDMZR (KS-20721) and RDL (KS-19522) couplers. A few months later I called for my refund. And sure enough, a check arrived covering all costs plus 7% simple interest. And because, as John described, there was a lot of equipment in the field that required that the coupler be there, Pacific Telephone let you keep the device in place. My friends and I used the RDMZR for multi-line conferencing (we just tied the audio pairs together and used the control leads for various control functions). But I always liked the RDL. I have always liked to fiddle with phones and electronics, but I have also always been a bit lazy. Why design my own telephone interface circuit when the RDL will do it all for you. It signals you that the line is ringing, you tell it when to answer. It then allows outgoing audio. When you are done with your outgoing announcement, you short a pair of wires and the RDL automatically provides a beep tone, reverses the direction of audio, and throws a relay to stop your outgoing tape and start your incoming tape. Despite what John Higdon says about audio loss, I still say that the answering machines I built with RDLs sounded better than most commercial machines on the market today (and definitely better than voice mail [which I now use]).