DSL on residential buildings.
Your comments remind me of how FCC limits began a few decades ago. As many may recall, in the days before "real" PCs, Playstations and the like, Coleman and others began marketing ping pong games one could play on their TV set. Since TVs had no direct inputs at the time, the small game box fed VHF signals to the TV antenna inputs, which were demodulated within the TV. The user was directed to remove the TV antenna leads to do this. However, it was not uncommon for a consumer to leave both the antenna and game leads attached to the TV. When the game was tured on and played, faint images of ping pong balls and paddles were transmitted via the outside antenna to neighbors' TV sets, prompting compliants. Due to this and related phenomena the FCC created EMI limits for digitally clocked systems employing a 10kHz clock or higher. You know the rest of the story. Oddly, our many electrical appliances not involving digital controls are not regulated, and create most of the EMI in a typical household. George --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: DSL on residential buildings.
We agree. The "gray area" arises from the fact that "residential" is not strictly defined. When the distinction was first made in subpart B, it hinged on whether equipment was sold for use in the home, not whether it was installed close to a home or farther away. I take the position that the need may be defined by whether the field strength from a class A device would be above the Class B limit at or inside a residential property. Whether Class B is enough is debatable. It is certainly not enough to protect non-broadcast communications, where received signals may be less than 20 dBuV/m. Cheers, Cortland On Wednesday, 20 Mar 2002, Hans Mellberg wrote >I may have gotten in on the tail end of the dicussion, but >here is my take on residential DSL. >The FCC rules are quite clear on equipment marketed to >residential environments, Class B. The DSL equipment >being sold to residences must comply with class B >limits notwithstanding office use. >small, non-rack mounted routers and switches are probably >still being argued as class A devices although most major >mfg make them already as class B. Eventually, when a lot >of homes incorporate hubs and routers then those will >also have to be class B. --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
Re: DSL on residential buildings.
I may have gotten in on the tail end of the dicussion, but here is my take on residential DSL. The FCC rules are quite clear on equipment marketed to residential environments, Class B. The DSL equipment being sold to residences must comply with class B limits notwithstanding office use. small, non-rack mounted routers and switches are probably still being argued as class A devices although most major mfg make them already as class B. Eventually, when a lot of homes incorporate hubs and routers then those will also have to be class B. --- Cortland Richmond <72146@compuserve.com> wrote: > > The reason for the Part 15 residential (Class B) limit is to protect > reception, and the levels prescribed are (arguably) low enough to do so. If > we allow higher levels, we are asking for service calls and perhaps > official attention. But (unless I am mistaken) it is now the USER who > responsible for interference generated by his Class A devices, and it's > perfectly legal for us to sell them to him. > > I recently spent some years working for a company that makes telecomm > equipment. I there encountered for the first time the "telco" point of view > (which is probably not uncommon). In the telephone world, the service > provider is responsible for everything up to the network interface. > Everything beyond that is the responsibility of the customer. Therefore, > some people assume that equipment installed prior to the NIC can be, and > should be Class A for Part 15. I have argued, with success, that this is an > error with potentially expensive consequences. > > Part 15 contains an exemption for equipment located within a facility - > even just a locked room, cabinet or vault - controlled by the telco. There > is an argument, which I make, that when we do this in a residential > building, if we are NOT Class B compliant, we may wish we had been. (Even > Class B is often not enough, and I have seen equipment meant for customer > use whose specification was well below the FCC limit.) And though our > employers' products may comply with Part 15 we are still liable for harmful > interference. > > However, emissions may be suppressed by other means than installing only > Class B equipment and this is often the way to go. The utility exemption > does make this easier. > > I personally believe that one may make a case for the mechanical room being > Class A. It often contains furnaces, motors, and many other unregulated > devices which generate high levels of radio and television interference, > and to impose a stricter standard on telecom equipment in the same place > seems a bit of a reach. > > But look at the environment! Will emissions reaching a customer location be > above the Class B limit? If so, then I would say due diligence requires > suppressing them further. A vault in a steel reinforced building's > basement is a different matter than a rooftop utility hut with TV antennas > just 3 meters away. If deployment entails a wide range of installations, > then it is probably best to suppress all of it to Class B, rather than > install Class B retrofit kits on a case-by-case basis. This is a decision I > believe has to be made when the product is proposed. > > > Regards, > > Cortland Richmond > (unemployed, and looking) > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" = Best Regards Hans Mellberg Regulatory Compliance & EMC Design Services Consultant By the Pacific Coast next to Silicon Valley, Santa Cruz, CA, USA 408-507-9694 __ Do You Yahoo!? Yahoo! Sports - live college hoops coverage http://sports.yahoo.com/ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher:
Re: DSL on residential buildings.
The reason for the Part 15 residential (Class B) limit is to protect reception, and the levels prescribed are (arguably) low enough to do so. If we allow higher levels, we are asking for service calls and perhaps official attention. But (unless I am mistaken) it is now the USER who responsible for interference generated by his Class A devices, and it's perfectly legal for us to sell them to him. I recently spent some years working for a company that makes telecomm equipment. I there encountered for the first time the "telco" point of view (which is probably not uncommon). In the telephone world, the service provider is responsible for everything up to the network interface. Everything beyond that is the responsibility of the customer. Therefore, some people assume that equipment installed prior to the NIC can be, and should be Class A for Part 15. I have argued, with success, that this is an error with potentially expensive consequences. Part 15 contains an exemption for equipment located within a facility - even just a locked room, cabinet or vault - controlled by the telco. There is an argument, which I make, that when we do this in a residential building, if we are NOT Class B compliant, we may wish we had been. (Even Class B is often not enough, and I have seen equipment meant for customer use whose specification was well below the FCC limit.) And though our employers' products may comply with Part 15 we are still liable for harmful interference. However, emissions may be suppressed by other means than installing only Class B equipment and this is often the way to go. The utility exemption does make this easier. I personally believe that one may make a case for the mechanical room being Class A. It often contains furnaces, motors, and many other unregulated devices which generate high levels of radio and television interference, and to impose a stricter standard on telecom equipment in the same place seems a bit of a reach. But look at the environment! Will emissions reaching a customer location be above the Class B limit? If so, then I would say due diligence requires suppressing them further. A vault in a steel reinforced building's basement is a different matter than a rooftop utility hut with TV antennas just 3 meters away. If deployment entails a wide range of installations, then it is probably best to suppress all of it to Class B, rather than install Class B retrofit kits on a case-by-case basis. This is a decision I believe has to be made when the product is proposed. Regards, Cortland Richmond (unemployed, and looking) --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
DSL on residential buildings.
Just making a quick check here. I'm seeing some product brochures out indicating some of these home units are class A. Am I missing something here, shouldn't that be class B. The fact its phone stuff (also carries the FCC part 68 stuff) can't override this classification correct? How about apartment buildings - is their mechanical room A or B? Gary --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
