why x-10 technology use a 120khz???

[dhouston]

hi,can someone tell me why x-10 technology use a 120khz of frequency to burst into a ac power line???

Because they could?

X-10 began more than 30 years ago and initially targeted the US market. Electric utilities, going back as far as the 1920's used "ripple control" which used (mostly) lower RF frequencies over their distribution lines for control and feedback. They probably wanted to avoid any conflicts with this. Household wiring acts like an antenna - rebroadcasting the RF into the air. The AM radio band starts at 535kHz and there are other important navigation bands bands below that to be avoided. http://www.jneuhaus.com/fccindex/10_khz.html#300_KHz Finally, there were not a lot of sophisticated ICs around in those days so they needed a frequency compatible with the discrete components that were available - the higher the frequency, the more difficult at that time.

This is all conjecture on my part but you can ask someone who was involved. Dave Rye is a VP at X-10 who was around at the beginning. I've found him to be accessible and helpful. I won't give you his email address as I'd hate to see him inundated with spam but you can probably find it with a Google search on "Dave Rye X-10".

[aratti]

Read the explanation at the link below

http://www.x10.com/support/technology1.htm