Originally written and posted 2 June 2001.
Content last modified Wednesday, 13 July 2016 .
External links last verified 6 February 2005.

Alignment of X10 modules and controllers

for optimum performance
Alert exclamation point in triangle IMPORTANT:This information is provided AS-IS, for informational purposes only, with no warranty whatsoever. Neither Sonic Purity nor anyone at Siber-Sonic.com can control your ability to successfully and safely utilize this information, and we accept no responsibility for anyone’s actions (beyond our own) related to the content of this website. X10 equipment utilizes the A.C. power line, which is dangerous. Do not attempt any of these adjustments if you have any doubt about your ability to work safely with household powerline-operated devices. It is your responsibility to know and understand common safety procedures, especially those involving electricity at potentially dangerous power levels!


Most X10 devices have one or more internal adjustments, most commonly related to the powerline carrier (PLC).

Modules typically have one transformer to optimize the reception of the 120kHz PLC signal. Old-style modules also contain a frequency adjustment for the IC.

The simpler controllers typically have both frequency and amplitude adjustments which affect the 120kHz PLC signal. More complex devices such as the RR501 transceiver may have 4 or more adjustments.

Why adjust? - To Improve Reliability

One may well ask, “Aren’t X10 modules correctly aligned at the factory? Why bother adjusting them?”

Well, first of all, given the low price of most X10 modules, not every one of them may have been optimally adjusted at the factory. Second, the transformers which couple the 120kHz PLC into and out of the A.C. powerline are affected at least slightly by the particular impedances of the particular wiring and connected devices at each particular location in each of our homes (and wherever else X10 devices may be used). Thus, marginally-triggering modules and controllers may both perform more reliably when adjusted to their particular locations. The alignment procedures on these pages take these considerations into account.

As an anecdotal testimonial, before i did any recent work on my X10 system, the CP290 controller usually failed to control several modules, including both a lamp and appliance module in the room just across the hall (albeit on the other powerline phase). This was true even with the .1µF cross-phase coupling capacitor in place in the breaker box.

After aligning the controllers and modules with the procedures described, AND cleaning the circuit breakers and their busbar and wire connections with Cramolin® R5 spray cleaner, the CP290 now reliably controls these modules, and indeed everything in the 2200 sq. ft. house and detached garage. Same with any combination of the other maxi- and mini-controllers, Sundowners, etc. with any modules.

In all honesty, while the alignments did noticeably improve the situation, the cleaning was essential for consistently reliable operation. Note that only two years prior, i had cleaned ALL the breakers/busbars/wires with Cramolin® R5. It cannot be overstated how important it is that all electrical connections throughout the structure are clean and tight for proper X10 operation!

It is truly a conundrum that the X10 system, designed to appeal especially to those not able/willing to remodel and add dedicated home automation wiring, requires for reliable operation a degree of twiddling which in some cases comes close to the effort which would have been put forth to install dedicated HA wiring in the first place! In our last home, a tiny 1927 rental house in Albany, California, U.S.A., even with cleaning and tightening and the cross-phase coupling the X10 system never did work reliably until (just before we moved out) the whole house was rewired in NM cabling. Then everything worked great.smiley

Not all wiring systems propagate 120kHz signals equally well, and it seems that the X10 system, reasonably enough, is designed for homes wired with NM cable (often called by the trade name Romex®) or wires in conduits. Old homes with open Knob and Tube wiring are likely to experience greater reliability issues, since the far greater spacing of the conductors will present a very different impedance to 120kHz signals intended to traverse closely-spaced conductors. Note that our current home is wired with Knob and Tube, yet with cleaning and alignment, the X10 system now works reliably.

Continue on to: X10 Alignment Procedures

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