kwf@ece-csc.UUCP (03/23/87)
Hello! I'm designing a system in which I want to use the power lines (outlets) in my home as the communication medium. My question is this: Does the power company get upset if you introduce a low-level (~1 volt peak-to-peak) high freq. (> 10 kHz) onto their lines (interior to your home). My concern is that this signal might screw-up synchronized machinery running on the same distribution transformer. (although 1 volt compared to 115 is not much). Is there a power-guy out there that might let me in on the no-no's. Thanks in advance! Kenneth Fernald (North Carolina State University)
parnass@ihuxz.UUCP (03/24/87)
x
Kenneth Fernald mentioned he was "designing a system in
which I want to use the power lines (outlets) in my home as
the communication medium."
Here are some wireless intercoms that use the AC power line
for communications. As you can see, my Radio Shack inter-
coms are rated at 50 milliwatts into the AC line. All fre-
quencies are listed in Megahertz.
intercom, wireless, Allied Knight-Kit
[KG-225]____________ 0.1360____-
" " 0.2150____-
intercom, wireless, Heathkit, fm
[GD-1114]___________ 0.2820____-
intercom, wireless, Lafayette, fm
[FM-50]_____________ 0.1600____ch C
" " 0.2000____ch B
" " 0.2400____ch A
intercom, wireless, Radio Shack, power 50 mw, fm
[43-212A]___________ 0.1600____ch B
" " 0.2000____ch A
" " 0.2300____ch C
" [43-214]____________ 0.1600____ch B
" " 0.2000____ch A
" [43-218]____________ 0.1600____ch B
" " 0.2000____ch A
" " 0.2300____ch C
intercom, wireless, Tele-Tender, power 50 mw, fm
[Comm-Call 300]_____ 0.2000____ch A
" " 0.2300____ch B
" " 0.2600____ch C
--
===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===
Bob Parnass, Bell Telephone Laboratories - ihnp4!ihuxz!parnass - (312)979-5414burris@ihuxz.UUCP (03/24/87)
In article <3271@ece-csc.UUCP>, kwf@ece-csc.UUCP (Kenneth W. Fernald) writes: > > I'm designing a system in which I want to use the power lines > (outlets) in my home as the communication medium. > There are already low cost intercom applications that use this principle. I believe that Radio Shack carries one or two models. Dave Burris ihnp4!ihuxz!burris
alab@ur-tut.UUCP (Daniel F. Luna) (05/08/87)
>My question is this: Does the power company get upset if you >introduce a low-level (~1 volt peak-to-peak) high freq. (> 10 kHz) >onto their lines (interior to your home). It is done all the time at AM frequencies (550kHz to 1600kHz) in the form of carrier current radio stations. In addition, the power company itself uses this medium on the high voltage system to transmit information between substations. The "BSR" system uses this method, as well. So as far as I know, it is OKEY DOKEY. The limiting factor is whether it will interfere. FCC rules say that if it interferes, you have to correct the interference, otherwise, it's ok. In the AM carrier current realm, there is a formula which determines signal strength at a specific distance. Distance is proportional to inverse frequency, so likely the audio range is quite ok. Industrial signalling equipment does this within complexes, and is also ok. -- Daniel F. Luna PC-Person. uucp: ...rochester!ur-tut!alab arpa: ur-tut!alab@rochester
wendt@arizona.UUCP (05/11/87)
In article <1286@ur-tut.UUCP>, alab@ur-tut.UUCP (Daniel F. Luna) writes: > >My question is this: Does the power company get upset if you > >introduce a low-level (~1 volt peak-to-peak) high freq. (> 10 kHz) > >onto their lines (interior to your home). I wonder if Tempest rooms (isolated computer rooms for classified stuff) typically include an isolation transformer to prevent transmitting information back from the computer along the power line? Alan W. U of AZ Computer Science
larry@kitty.UUCP (Larry Lippman) (05/13/87)
In article <1708@megaron.arizona.edu>, wendt@arizona.edu (Alan Lee Wendt) writes: > > >My question is this: Does the power company get upset if you > > >introduce a low-level (~1 volt peak-to-peak) high freq. (> 10 kHz) > > >onto their lines (interior to your home). > > I wonder if Tempest rooms (isolated computer rooms for classified stuff) > typically include an isolation transformer to prevent transmitting > information back from the computer along the power line? Not only are there isolation transformers for AC power, but each hot and neutral leg of any AC power feed passes through some pretty hefty "feed-through" capacitors to further attenuate any RF energy. Data communication lines are optically isolated whereever possible, using simple current loop/optoisolator circuits for low-speed data lines, with more sophisticated isolation techniques being used for circuits greater than 19.2 kbps. As one can intuitively imagine, the use of actual fiberoptic data lines increases the communications security in this environment. ANY electrical penetration to such a secure area is isolated; this includes such circuits as HVAC control, physical security control, etc. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rocksanne|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
faunt@spar.UUCP (05/13/87)
In article <1708@megaron.arizona.edu> wendt@arizona.edu (Alan Lee Wendt) writes: > >I wonder if Tempest rooms (isolated computer rooms for classified stuff) >typically include an isolation transformer to prevent transmitting >information back from the computer along the power line? > At least the ones I was in, and those that had telephones had them on opto-isolators.