Q101. What is X10?

X10 is a communications protocol for remote control of electrical devices.
It is designed for communications between X10 transmitters and X10
receivers which communicate on standard household wiring. Transmitters and
receivers generally plug into standard electrical outlets although some
must be hardwired into electrical boxes. Transmitters send commands such
as "turn on", "turn off" or "dim" preceded by the identification of the
receiver unit to be controlled. This broadcast goes out over the
electrical wiring in a building. Each receiver is set to a certain unit
ID, and reacts only to commands addressed to it. Receivers ignore commands
not addressed to them.

Note that "X-10" is a trademark of X-10 (USA) Incorporated an possibly of
X-10 Home Controls Incorporated (in Canada) as well. This FAQ uses "X10"
unless referring specifically to a product of the holder of the "X-10"

Q102. What sort of X10 transmitters exist?

The simplest X10 transmitter is a small control box with buttons. The
buttons select which unit is to be controlled, and which control function
is to be sent to the selected units (e.g. "turn on", "all units off", etc).
There are also clock timer transmitters which can be programmed to send X10
commands at certain times. Some of these can be programmed with buttons on
the timer; some must be connected to a computer to select the times. There
are other special purpose transmitters that send certain X10 commands at
sunup or sundown, upon detecting movement, or as commanded by tones over a
telephone. This is not an all inclusive list, and more detail on specific
transmitters is given in Section 2.

Q103. What sort of X10 receivers exist?

The simplest X10 receiver is a small module with an electrical plug (to
connect to a standard wall outlet), an electrical outlet (to provide
controlled power to the device it's controlling) and two dials (to set the
unit ID code) on it. An appliance module has relay inside which switches
power to its outlet on or off in response to X10 commands directed to it. A
lamp module is similar, but has a triac instead of a relay and will respond
to dimming commands as well as on or off commands. Other receivers can be
wired into wall outlets or into lamp fixtures. Note that the standard wall
switch (X10:WS467) is a receiver, not a transmitter; it does not transmit
X10 commands, and only takes action when it receives the appropriate X10
command or local button-push.

Q104. How many different units can X10 handle?

X10 specifies a total of 256 different addresses:  16 unit codes (1-16) for
each of 16 house codes (A-P). Normally a transmitter is set to a certain
house code (generally selectable by means of a dial) and so can control at
most 16 unit codes. There is no restriction on using multiple transmitters
each set to a different house code on the same wiring. Also, several
receivers could be set to the same house code and unit code so a single
command issued by an X10 transmitter could control multiple receivers in

Q105. Who makes X10 components?

Many different companies either make and/or distribute X10 components
under different names. Some types are sold by more than one company
(probably made by same OEM). Some are specific to only one company. Not
all companies handle the complete range of components. Some companies
selling X10 components and their associated product names are:

 Radio Shack:
        Plug 'N Power

        Decora Electronic Controls

        Leviton Mfg. Co. Inc.
        59-25 Little Neck Pkwy
        Little Neck, NY  11362-2591

        Leviton Manufacturing of Canada
        165 Hymus Blvd
        Point Claire, QC  H9R 1G2

        Light Maker

 X-10:  Powerhouse

        X-10 (USA) Inc.
        91 Ruckman Road, Box 420
        Closter, NJ  07624-0420

        X-10 Home Controls Inc.
        1200 Aerowood Drive, Unit 20
        Mississauga, Ont  L4W 2S7

	X-10 Europe
	93 rue de Prony
	F-75017 PARIS
        Voice 33-1-42678877
	Fax 33-1-42679309

 Home Automation, Inc.
	2709 Ridgelake Dr.
	Metairie, LA 70002
	Phone:   504-833-7256
	Fax:     504-833-7258

 Powerline Control Systems
	9031 Rathburn Avenue
	Northridge, CA 91325
	Phone: 818-701-9831
	Fax:   818-701-1506

Q106. Who sells X10 components?

The following companies are alleged to sell X10 components in North
America. See Q108 for outside North America. Listing in this FAQ is not
an endorsement or recommendation of any kind:

If you are a dealer and wish to be listed here then please send me an
entry formatted _exactly_ like those below.

 Advanced Control Technologies
 Voice:  317-337-0100
 FAX:    317-337-0200

 Advanced Home Automation Inc.
 186 Raglan Road West
 Oshawa, ON
 Voice:   905-655-5355
 Orders:  800-265-6938
 Fax:     905-655-5356
 BBS:     905-655-5844

 Advanced Services Inc.
 4 South Russell Street
 Plymouth MA 02360
 Orders:  800-263-8608
 Voice:   508-747-5598
 Fax:     508-747-5598

 Baran-Harper Group Inc.
 340A Alden Road,
 Markham, ON  L3R 4C1
 Help/Info:    905-946-2451
 Fax:          905-479-0455
 BBS:          905-479-0469

 Canadian Control and Automation Ltd
 7 Wincanton Rd.
 Markham, ON   L3S 3H3
 Phone:   905-470-9121
 FAX:     905-568-3658

 Complete Home Automation
 Phone:   800-766-4226 (doesn't work in Canada)

 Home Automation Laboratories
 5500 Highlands Pkwy, Suite 450
 Smyrna, GA 30082-5141
 Orders:  800-466-3522
 Catalog: 800-935-4425
 Help:    404-319-6000
 Fax:     404-438-2835 (is this the right number?)
          404-410-1122 (is this the right number?)
 BBS:     404-319-6227 (300-14.4,8,N,1)

 Home Automation and Security
 286 Ridgedale Ave.
 East Hanover, NJ 07936
 Orders:  800-254-5950
 Help:    201-887-1117
 Fax:     201-887-5170

 Home Automation Systems, Inc.
 151 Kalmus Drive, Suite M6
 Costa Mesa, CA 92626
 Orders:  800-762-7846 (doesn't work in Canada)
          800-367-9836 (supposedly works in Canada, but doesn't really)
 Help:    714-708-0610 (also for orders from outside US)
 Fax:     714-708-0614

 Home Control Concepts
 9520 Padgett St. Suite 108
 San Diego, CA 92126
 Orders:  800-422-4024
 Help:    619-693-8887
 Fax  :   619-693-8892

 Hybrid Technical Systems, Inc.
 4765 Franchise Street
 Charleston, SC 29418
 Orders:     800-289-2001 (doesn't work in Canada)
 America Online:  HybridTech
 Compuserve:    71561,2604

 JaMar Distributing
 1292 Montclair Drive,
 Pasadena, MD  21222
 Orders:     800-477-4181
 Fax:        410-437-3757
 Help:       410-437-4181

 JDS Technologies
 16750 W. Bernardo Drive
 San Diego, CA 92127
 Orders:     800-983-5537
 Help:       619-487-8787
 Fax:        619-451-2799

 Marrick Limited
 P.O. Box 950940
 Lake Mary, FL 32795
 Voice:      407-323-4467
 Fax:        407-324-1291
 BBS:        407-322-1429

 4 Park St.
 Vernon, CT  06066
 Orders:     800-635-3355 (doesn't work in Canada)
 Phone:      203-871-6170
 Fax:        203-872-2204

 MoTron Electronics
 310 Garfield St., Suite 4
 PO box 2748
 Eugene OR 97402
 Tel:        503-687-2118
 Fax:        503-687-2492
 Orders:     800-338-9058

 Mountain Vista Supply, Inc.
 4108 La Linda Way
 Sierra Vista, AZ  85635
 Phone:      602-459-0002
 Fax:        602-458-3472

 Worthington Distribution
 36 Gumbletown Road
 Paupack, PA 18451
 97 Fairmount Road
 Tewksbury, NJ 07830

 Orders: 800-282-8864
 Tech support: 717-226-8864
 Fax: 717-226-0470

Q107. How do I solve the most common X10 problems?

There is a common problem that you may encounter in setting up your home
with X10 modules. This happens mostly in larger homes, say larger than
2000 square feet (185 square meters). The symptoms are that some receiver
modules may not work when commanded from some transmitters, or they may
only work sporadically.

This could be caused by too much isolation between the two sides of the
power line (assuming North American wiring standards):  a transmitter on
one side will not transmit reliably to a receiver on the other side. Try
your X10 system with and without your electric stove turned on; turning the
stove on may bridge both sides of the power line, but is not the
recommended permanent solution. A better way would be to install a signal
bridge which is available as a commercial product. See section 2 below for
details. An alternative solution is to install a 0.1 microfarad capacitor
(240 VAC or 600 VDC) across the 220 volt line "hot-to-hot". A qualified
electrician can do this across any 220 volt double pole breaker. This will
bridge the signal from one side to the other.

This could also be because the distance from the transmitter to the
receiver is too great and the signals are two weak to activate the
receiver. If moving the transmitter does not work or is not feasible, the
solution may be to install a signal amplifier. This is available as a
commercial product. See Section 2 below for details.

Noise blocks or noise filters may solve other more obscure problems (false
ON/OFF signals, for example), often caused by TVs or wireless intercoms.
Locate interference sources by unplugging them one at a time. See details
on commercially available noise blocks and filters in Section 2 below if
moving the transmitter away from interference sources does not work or is
not feasible.

> See next paragraph
> If a WALL OUTLET 220V, 15A (X10:HD243) or WALL OUTLET 220V, 20A (X10:HD245)
> doesn't seem to work in an apartment or office building, that may be
> because the building has a three phase power system and the X10 outlets are
> designed to work on a single (split) phase system such as found in a home.
> There is no solution to this.

New information (Jul 95). The X10 protocol apparently sends signals at
the zero crossing of the AC line voltage and then at 60 degrees and at
120 degrees after that (in other words, three times every half cycle
corresponding to the zero crossing of the other two phases). This is
designed to make X10 compatible with three phase power situations.

Some power strips that have filters in them to protect electronic equipment
effectively filter out X10 signals. Also appliances such as televisions
or other audio/visual equipment may have a capacitor across the AC line
to filter out high frequency noise. X10 signals appear as high frequency
noise to these capacitors and are thus attenuated. Cheaper power strips
that protect against voltage spikes only do not affect X10 signals. Try
moving X10 transmitters or receivers from power strips to a standard
outlet if they don't seem to be working.

Another common problem with X10 devices is not reading the documentation
that comes with them. People still insist on trying to use dimmer switches
or lamp modules on electric fans or fluorescent lights (symptom can be
fire), or trying to control low wattage lamps (symptom may be unreliable
operation for less than 50W for some modules). Solution:  RTFM. See also

Q108. Will X10 work on 220/240V?

There are X10 receiver modules designed to control 240 volt loads, but only
where these are part of a standard North American wiring system, e.g. for
the electric stove or electric drier. See section 2 below.

Knowledge of how X10 works on anything else than 60 Hz 110V is a bit hazy
in North America. The following companies are reputed to sell X10 devices
for European use:

 Busch-Jaeger Elektro GmbH
 P.O. box 1280
 D-5880 Luedenscheid
 Phone: +49 2351 956-0
 Fax  : +49 2351 956-694

 Celtel Ltd
 P.O. Box 135
 United Kingdom RG25 2HZ
 Phone:  01256 64324
 Fax:    01256 818064

 Cirkit Distribution Ltd.
 Parks Lane
 Broxbourne, Herts
 United Kingdom EN10 7NQ
 Phone:   01992 441306
 Fax:     01992 471314

 Laser Business Systems Ltd.
 16, Garthland Drive
 Arkley, Barnet
 Hertfordshire EN5 3BB
 United Kingdom
 Tel: +44 181 441 9788
 Fax: +44 181 449 0430

 Smart House Systems
 3 Buchanan Street
 United Kingdom KA30 8PP
 Tel:   0141-848-6700
 Fax:   0141-889-1045

 WDC Home Automation
 30, The Broadway
 Thatcham, Berkshire
 United Kingdom RG13 4HX
 Phone:   01635 866707
 Fax:     01635 871141

The following companies are reputed to sell X10 devices in Australia:

 Brylyn Enterprises(Bryan Mason)
 Broadbeach, Queensland
 Phone:   617-531-5179

 CEBus Australia
 PO BOX 178
 Greensborough VIC 3088
 Phone:   03 467 7194
 Fax:     03 467 8422

 Midac Technologies
 Upper Monkerai
 New South Wales 2415
 Phone:   049 94 7069
 Fax:     049 94 7039

 The Smart Company
 5 Mouat Street
 PO Box 127
 Fremantle, Western Australia  6160
 Phone:  09 430 8887
 Fax:    09 430 8886

Q109. How do I send and receive X10 signals with my computer?

The easiest way of giving your computer some control over X10 modules is
via the CP290 Home Control Interface. This is a small box that connects to
a standard RS-232 serial port and has its own internal battery backed up
seven day clock. It is sold with software to work with a PC, Mac, Apple ][,
or Commodore 64/128, and comes with the appropriate serial cable (the CP290
box itself is the same for all). Once you set up to 128 events (on, off,
dim) using your computer, you can turn off the computer and the box will
transmit scheduled X10 commands on a daily or weekly schedule. The CP290
also has an "immediate" mode to send X10 commands from the computer to X10
receivers. Details on programming the CP290 are in Section 4.

There are also other X10 modules to interface computers directly to the
power line to send and/or receive X10 commands. These are the PL513 (send
only) and the TW523 (send and receive).

The TW523 is a low level two-way interface to the power line. It
contains a PIC controller to decode incoming signals and store them for
transmission to the host computer. (The PIC is a family of
microcontrollers from Microchip Technology (before that, from General
Instrument).  They come in packages ranging in size from 18 pins up to
40 pins with a whole gamut of features.  They have nothing to do with
X-10 per se, but they work wonderfully for doing low-level X-10
control). It's essentially a 120KHz modulator and demodulator, with just
enough smarts to recognize a valid X-10 command code. Due to the tight
timing requirements and lack of drivers, applications are limited to
systems developers and experienced hobbyists willing to code in

The computer interfaces to the TW523 through an RJ-11 modular phone jack
which has the following signals: signal (not AC) ground, receive output,
zero-cross output and transmit input. All signals are optocoupled, and the
outputs are open-collector. A logic high (greater than 4V) on the transmit
input modulates the AC line with the 120KHz carrier wave. The zero-cross
output is a square wave coincident with the 60Hz AC line. The receive
output is an envelope of the X-10 signal, and is low when the 120KHz signal
for `bit=1' is present during a valid code.

The signal applied to the transmit input must encompass all of the bits for
all 3 phases of the line (i.e. 3 bits per half AC cycle). The computer
must follow the full transmission protocol detailed in Section 3 of the
FAQ, but only needs to send the proper envelope for the transmission as the
TW523 converts the digital envelope into bursts of 120KHz carrier.

The receive output is buffered through the PIC in the TW523. The first
valid X-10 code cycle on the AC line alerts the PIC (and is lost to the
controlling computer). During the second code cycle (all codes in X-10
protocol are sent twice), the TW523 outputs a low when there is 120KHz
carrier on the AC line, and only during the bit time for the local AC
phase. The signals for the other two AC phases are not echoed to the
controlling computer. The output is open-collector at all other times.
The logic is reversed; when there's a valid `bit=1' (120KHz carrier), the
output is low, and high otherwise. Since the TW523 responds to all signals
on the AC line, it also echoes any sent by the controlling computer,
allowing for collision detection similar to that used by the Ethernet
protocol (CSMA/CD).

[Question: does it output only the second transmission when echoing local

These units may be supplied with parallel or serial port adaptors. These
use handshaking bits in non-standard ways, so normal serial and parallel
port drivers are not of any use.

See also Q115 for information on PLIX, which simplifies interface
requirements considerably.

Q110. Where do I get X10 software for my computer?

The CP290 Home Control Interface comes with software for either IBM PC,
Mac, Apple ][, or Commodore 64/128. This is rudimentary, but functional.

Baran-Harper Group Inc in Ontario runs a bulletin board that has a good
selection of software for the CP290 and TW523. Their BBS number is 905-
479-0469. Also try BBS listed for other companies in Q106 above.

Other sources:

 FTP:   (CP290) (UNIX CP290)    (CP290 source+ for VMS, Atari ST) (CP290 source)

 WWW:   (CP290 source+ for VMS, Atari ST)

Q111. Where do I look for more information on X10?

Try the following:


 Circuit Cellar Ink
 4 Park St
 Vernon, CT  060663233
 Phone:   203-875-2751
 FAX:     203-872-2204
 BBS:     203-871-1988

 Electronic House [is this the editorial address???]
 EH Publishing
 P.O. Box 339
 Stillwater, OK 74076-9923
 Phone:   405-624-8015  (800) 375-8015 ???
 FAX:     405-743-3374

 Electronic House [is this the address for subscriptions only???]
 P.O. Box 7972
 Riverton NJ 08077-8672
 Phone:   508-358-3400
 FAX:     508-358-5195

 Electronic House Magazine[...then what address is this???]
 304 Boston Post Road
 Wayland, MA 01778
 Phone:   508-358-3400
 Fax:     508-358-5195

 Home Automator
 2258 Sandy Lane
 Mebane, NC  27302
 Voice:   910-578 9519
 FAX:     910-578-0012
 Notes:   Free sample issue available, ask for it via voice, FAX or email.

 Practical Home Automation magazine
 3043 South Laredo Circle
 Aurora, CO USA 80013-1805
 Phone:   303-699-5541
 FAX:     303-766-2696
 BBS:     303-680-3864 (8N1, 2400-9600 V.32)


_The Complete Guide to Home Automation_ David Alan Wacker 1993 Betterway
Books Cincinnati, Ohio ISBN 1-55870-301-2. Review by Benjamin Lonske
follows.  Excellent introduction to Home Automation.  Chapters on
Wiring, X-10, Security Systems, Environmental Control, Whole House A/V,
Water Management, Whole House Automation, PC-Based Automation, SMART
HOUSE.  Good pictures and descriptions but not a how-to book.  One
negative: some descriptions about specific systems basically unfiltered
info from manufacturers.

_Controlling the World with Your PC_ by Paul Bergsman. About $30.
Discusses input and output interfacing through the parallel port, and
lots of things that you can then do to use that port to connect your PC
to the world.  It's available from Hightext, PO Box 1489, Solana Beach,
CA  92075, phone 800 247-6553.

_How to automate your home_ David Gladdis 2nd Ed. 1991 David
Gladdis(pub) ISBN 0-9632170-0-3. Available from Baran-Harper and
possibly other X-10 mail-order companies


Electronic House publishes an annual resource guide listing many home
automation suppliers and manufacturers.

Some dated but still good information can be obtained by sending email


Do a web search from your web browser for the latest sources.

 These are not X10 but you probably want to know about them.

Mailing lists:

 The jds users mailing list is for users of JDS Timecommander and
 Homebase products to share experiences and information.  Send mail to with 'subscribe jds-users' unquoted in
 the body.

X10 Expertise for hire:

 Canadian Control and Automation Ltd
 7 Wincanton Rd.
 Markham, Ontario CANADA
 L3S 3H3
 Phone:   905-470-9121
 FAX:     905-568-3658
 Custom engineered home automation systems, security,fully distributed
 A/V, home theater, energy management solutions, also SmartHouse(tm)

 T. Brusehaver
 Empowered Home
 10608 Alabama Circle
 Bloomington, MN 55438
 Phone:   612-887-1342
 X10 hardware and software, development in other areas of home automation,
 energy saving devices, smart occupancy sensors, infrared control

 Rick Sloan
 IntelliHome Controls
 15 - 8 Deerfield Drive
 Nepean, ON, CANADA  K2G 3R6
 Phone:    613-723-1427
 FAX/BBS:  613-723-2370
 X10 hardware and software, development in other areas of home automation,
 energy saving devices,smart occupancy sensors, products for disabled
 persons, infrared control

Q112. How should I design the wiring of my new home to accommodate X10?

Most X10 receivers and transmitters can be plugged or wired into
conventional wiring in any home without any special preparation or design.
However, if you have the luxury of designing the wiring in your home before
it is built, there are a few things you may wish to consider.

A conventional light switch is wired into the circuit between the power
panel and the light it controls. Wiring conventional three-way (or more)
switches for use at the top and bottom of the stairs for example, takes
special wiring and foresight. There are X10 wall switches to replace
conventional switches in conventional wiring, both for simple on/off and
three-way control. See Q114.

You may wish, however, to put dedicated control modules (see LEV:6375,
LEV:6376 in Section 2) into built-in light fixtures and wire these fixtures
directly to the power supply with no conventional switch. You could then
turn the lights on or off from X10 transmitter anywhere in the house. Of
course, you may wish to put in a conventional switch somewhere so you could
manually enable/disable the light fixture independent of X10 on/off

You would probably want to install wall mounted controllers (see LEV:6319
series) instead of light switches at convenient places like entrances or
stairways. The wiring for these wall mounted controllers is just like the
wiring for a power outlet: two wires direct to the power supply. This is
NOT the same as wiring for a conventional light switch. By changing the
settings on the control modules and the wall mounted controllers you can
link any switch to any light. Any light can be controlled in a three-way
(or four-way, or more) manner just by adding more wall mounted controllers
wherever convenient.

A motion/sunup/sundown detector (e.g. X10:PR511) is a good addition to any
house. You will probably want to wire this in a conventional circuit
controlled by a conventional light switch. This way you can disable it
(stop it from sending X10 signals) if you have to.

Other things you could consider are dedicated outlets in convenient
locations for Christmas lights (few house builders ever think of this).
This will avoid running extension cords out the garage or off the outdoor
light fixtures. With these controlled by X10, you could then have your
X10:CP290 turn them on or off as required. In Canada and other
occasionally frigid climates you might consider controlling the outlet for
your block heater by X10, but watch that the power drawn by the heater
doesn't exceed the capacity of the X10 receiver.

You may wish to document clearly how you have wired the house in case you
ever sell it. It may not be obvious to the next occupant, or to any
electrician he hires to "fix" things.

Don't forget telephone wiring. For the ultimate house, you'll want at
least one unlisted telephone line for remote control of your house from a
DTMF phone anywhere in the world. This will take a telephone interface
such as X10:TR551 or LEV:6325. While this might see like an expensive
luxury, think of what you could do by calling to turn off your fax machine,
and turn on your computer so that you could call it (on a separate line) to
transfer data. When done, you turn it off (or better, have it turn itself
off by sending the proper command to its X10 interface) and turn on the fax
machine again.

Also don't forget to allow for future expansion. Run empty conduit from
each room to a central location (AKA wiring closet). Class 125 PVC water
pipe is cheaper than Schedule 40 conduit. That way you can snake wires
to each room without climbing into the attic, under the house or running
wires under carpets, etc. Eventually you will want to add something new
(motion detectors and other security related items, temperature sensors,
computer networks, serial terminal lines, another phone line, TV,
speaker wires, etc etc etc). While you are at it, run a few 8 conductor
cables to each room. Terminate these cables and the conduit in a couple
of electrical outlet boxes with blank covers. X10 can't do everything :-)

See also:

Q113. How do I control fluorescent and halogen lights with X10?

Lamp modules and standard X10 wall switch (e.g. X10:WS467) generally do not
work well anything other than incandescent lights. There are several
reasons why this is so.

Both lamp modules and wall switches cut out part of the power sine wave to
dim the lights that are connected to them; the waveform available at the
load is no longer a simple sine wave, but a sharply-truncated version of a
sine wave. Even at full brightness, there is some power cut [Can anyone
confirm this?]. This is not too critical for a simple incandescent light.
For a compact fluorescent lamp that has some electronic circuitry in the
base to drive it, however, this is not a good idea since the circuitry is
designed around the expectation of a stable waveform at standard voltage.
Trying to dim a compact fluorescent by modifying the input power supply is
like trying to turn down the volume on your radio by putting it on a dimmer
circuit. It may sort of work with unpredictable results, but cause damage
to the load being dimmed.

Standard lamp modules and appliance modules have full access to house
current since they are plugged directly into a power outlet. Standard X10
wall switch modules, however, rely on getting their power from current
leaking through the filament of the incandescent bulb(s) in the circuit
they control even when the bulb is off. If the load they control is not a
standard incandescent bulb, there may be no (or not enough) current to the
switch and it may not operate as designed. This may be especially true for
fluorescent bulbs, or special power saving bulbs that have diodes built
into the base.

As noted above, the voltage output from lamp modules and standard X10 wall
switches is not a pure sine wave. Transformers are generally designed for a
certain frequency or range of frequencies (e.g. 50-60 Hz). They may not be
able to handle the higher frequency harmonics present in the sharply
truncated sine wave output from a lamp module or wall switch. As a result,
they may heat up and/or burn out. This is true of halogen or fluorescent
lamps that have an integrated transformer. It's true of any device with a
transformer (e.g. some radios and computers) or with a motor (e.g. garage
door opener or electric fan).

A standard APPLIANCE MODULE (X10:AM486) may work for loads that are other
than incandescent lights. Note that when used with a compact fluorescent
bulb, the local control mode in the appliance module often senses a small
current flow and keeps turning on. See Section 5 on defeating local
control. Using an appliance module on a halogen light should work in most
applications, but will not permit remote dimming. If the light has a
built-in dimming control, this can still be used.

There are special modules designed for fluorescent lights and other loads.
Some of these may be in wall switch form but require a neutral power
connection (not all existing wiring designed for a manual on/off switch
have the neutral connection). Others (e.g. LEV:6375) wire directly into
the light fixture and rely on control from some X10 transmitter (e.g.
LEV:6319-4 series). Halogen flood lights work fine in MOTION DETECTOR
(X10:PR511, LEV:6417).

There has been some success reported in using the standard X10
incandescent wall switch for controlling halogen lights that do not have a
transformer in the light fixture. There are many types of halogen bulbs;
mileage may vary. Use at own risk.

Despite the information above and warnings on X10 lamp modules and wall
switches that they be used only for incandescent loads, people persist in
trying to use them for other loads. There are unconfirmed reports that
doing so will cause the module/switch to catch fire (luckily this rarely
happens more than once for a single installation). One should be very sure
that one understands the full implication of going against the
manufacturers' recommendations when directly connecting a device to the
main power supply which will be left unattended in a valuable home.

See also notes on LEV:6291 WALL SWITCH MODULE. This is like a standard
wall switch that will control any load on an off (no dimming). It
incorporates a relay like an appliance module.

Q114. Can I use X10 in a three-way light switching application?

The way lights are normally wired is with a single on/off SPST switch.
When the contacts are closed, the light is on; when open, the light is off:

              /                |
        -----*                 |
               *(off)        LIGHT

In a three-way switching application, a pair of SPDT switches (often at the
top and bottom of stairs) are wired so that the light can be turned on or
off from either switch. (This is sometimes called two-way switching.)
Note that for three-way switching, neither the switches nor the wiring are
the same as for normal on/off switching:

        -----*                    *---------
                                 /          |
               *----------------*         LIGHT

In a situation where a light is already wired for three-way switching, X10
can easily be used. Install the WALL SWITCH 3-WAY KIT (X10:WS4777) -- see
section 2 below. This contains one WALL SWITCH 3-WAY (master) and one WALL
SWITCH 3-WAY REMOTE. Put the master in place of one switch and the remote
in place of the other, wiring carefully as shown in the instructions that
accompany the kit. Note that this is for incandescent lights only and not
for appliances, motors or fluorescent lights.

In fact, this will work where lights are already wired for four- or more-
way switching as well. All you need is one additional WALL SWITCH 3-WAY
REMOTE (available separately) to replace each additional SPDT conventional

If you are wiring a circuit with the intent of using X10 in a three-way (or
more) light switching application, don't wire it as shown above. A much
simpler and more flexible method is described in Q112.

Q115. What is PLIX?

PLIX stands for Power Line Interface to X-10. It is an 18 pin DIP ASIC
which performs all the timing and decoding necessary to interface a PL-513
transmitter or a TW-523 transmitter/receiver to a microprocessor's TTL I/O
port. In a nutshell, it does all the bit twiddling necessary to send and
receive X-10 commands using a TW-523, simplifying the interface for home
automation software. This allows even interpreted BASIC to send and
receive commands to X-10 devices.

The PLIX chip can send and receive one command at a time. It can receive
and buffer one X-10 command "in the background" (i.e. without any attention
from the host processor) but if a second command comes in before the first
is read the earlier data is overwritten.

The PLIX Evaluation Board kit (PLIX-EKit) is a PLIX chip, printed circuit
board, and all required components. You must assemble it. By hanging a
PLIX-EKit off the parallel printer port on your IBM PC and running the
appropriate software, you can send and receive X-10 commands from your IBM
PC. The PLIX chip also includes an AC Power Failure detect line, which on
the PLIX-EKit is wired to generate an interrupt request to the host PC in
the event of a power failure. As a minimum setup you would probably need a
TW-523 interface and a "straight through" modular telephone cord, plus some
kind of power supply (either a 9V battery or a simple power pack) and a
case if you need it.

The PLIX chip comes with some simple software in BASIC, and there is sample
C code available via anonymous ftp from
Knowledge of BASIC, Pascal, or C would be more than sufficient to do your
own programming.

The PLIX chip and data sheet is $20 + shipping, and the EKit is $39 +
shipping, both available from the MicroMint.

Q116. Can I use X10 components outside?

>From time to time you may wish to control loads outside your home with X10.
Generally this should be a WALL OUTLET (X10:SR227, LEV:6227) or an
APPLIANCE MODULE (X10:AM466). There are two considerations you must bear
in mind in installing these.

First, the X10 device must be protected from moisture. An appliance module
should not be put outside; you might want to put it in your garage or
garden shed (assuming you have power in these locations) and run an
extension cord to the load out under the door. A more flexible approach
would be to put an X10 wall outlet in an existing outside electrical box.
This must be a weather proof box with tight cover. If you intend to leave
something plugged into it for long periods of time, you will have to find
or make some kind of cover that protects the X10 wall outlet from moisture.

Second, the X10 device should be on a circuit protected a ground fault
circuit interrupter (GFCI, sometimes known as GFI). These are special
outlets that shut down very quickly when they detect some leakage current.
These can put in serial with an appliance module (appliance module plugged
into GFCI outlet), or in parallel (X10 wall outlet wired on load side of
GFCI outlet) as shown below (North American wiring assumed):

  house current   _____         _____
  ________________|* *|---------|* *|  X10 appliance module (plugged into
  ________________| * |---------| * |   GFCI outlet, protected from
  ________________|   |---------|   |   elements)
            (line)|* *|         -----
                  | * |          ||+-------------
                  -----          |+--------------  load (plugged into
                                 +---------------   appliance module)

  house current   _____           _____
  ________________|* *|___________|* *|
  ________________| * |___________| * |
  ________________|   |___________|   |----------  load (plugged into
            (line)|* *|(load)     |* *|----------   X10 wall outlet)
                  | * |           | * |----------
                  -----           -----
                  GFCI           X10 wall
                 outlet           outlet (in weather proof box)

> See below
> One final warning is about installing the X10 wall switch in an area
> where it will get cold. Apparently the triac in it doesn't work at low
> temperatures. For this reason, you should avoid even putting it in an
> outside wall.

New information (7/95) Many people have had no problem running X10
devices in sub zero temperatures. X10 specifies that the devices
will run from . X10 devices do consume some power at all times and
thus generate some heat. This may affect the working temperature range.

Q117. What are the various combinations of X10 wireless receivers and
transmitters that work together?

WIRELESS TRANSMITTER (X10:RT504, LEV:6313, RS:61-2560) will work with
To control 16 units, use two X10:RR501 (one set to 1-8, the other set to 9-
16) or one X10:TM751.

The surface mount two, three and four button WIRELESS TRANSMITTERS
(X10:RW684, X10:RW724, X10:RW694 respectively) will work for all codes
(X10:RR501, LEV:6314), respectively they will only work for units 1-2, 1-3,
or 1-4 if the receiver is set for 1-8; or 9-10, 9-11, or 9-12 if the
receiver is set for 9-16.

The WIRELESS TRANSMITTER (X10:KC674) works for all codes with WIRELESS
RECEIVER (X10:TM751). With the WIRELESS RECEIVER (X10:RR501, LEV:6314), it
will only work for units 1-2 with the receiver set on 1-8.

All the transmitters work with X10 security systems to some degree. Check
before investing. You should not use the WIRELESS RECEIVER (X10:TM751 or
X10:RR501, LEV:6314) if you have an X10 security system (their timing is
slightly different and the signals they put on the power line will
interfere with each other). You should not have two wireless receivers of
any type in close proximity (e.g. in same AC power bar) to each other
(their local oscillators may interfere with each other).

The bottom line is that the WIRELESS RECEIVER (X10:TM751) is much more
flexible than the WIRELESS RECEIVER (X10:RR501, LEV:6314) strictly for
control purposes. If you already have an X10 security system, you should
not need a separate wireless receiver.

Q118. How do I make the motion detector floodlight unit work properly?

MOTION DETECTOR (X10:PR511, LEV:6417) is a useful device that functions as
both X10 receiver and transmitter. It contains a sensor head to detect
motion, an X10 receiver to turn on the attached flood lights, and an X10
transmitter to turn on up to four X10 units when motion is detected or four
other X10 units at dusk and off again at dawn. It also has a shutoff
control with a variable timer to turn the lights (and remote units) off
after motion has stopped. It has a photocell control with variable
sensitivity to determine when dusk and dawn occur.

The most common problems with the motion detector can be solved by reading
the short owner's manual that comes with it. This may seem obvious, but
the answers to the most frequently asked questions are in fact in the

If the detector does in fact detect motion during daylight hour and you
want it to do so only at night, you need to adjust the DUSK control. Note
that each time you change this, the new value will not become effective
for ten minutes, or one minute if you turn the power off and then on again.

The flood lights on the detector be triggered on either by motion (turns off
after a set time), or by darkness (turns off in the morning). This mode is
set on the THIS UNIT switch, either SENSOR (for motion) or DUSK (for
darkness). Halogen floodlights work fine with this device.

Independent of the setting of the THIS UNIT switch, the detector can turn
on and off up to four remote X10 units when it detects motion. These units
are the four units that follow in numerical sequence from the unit number
of the detector. Thus if the detector is UNIT 1, when motion is detected
(sensitivity controlled by RANGE control), the detector will send X10
signals to turn any or all of (individually selectable) UNITs 2, 3, 4, and
5 ON for the same house code, and turn them OFF again after the selected
time (controlled by TIME DELAY control) has elapsed. As a second example
of the unit codes, if the detector is UNIT 14, then any or all of UNITs 15,
16, 1 and 2 for the same house code can be triggered for motion detection.
To reiterate, the detector can detect motion and trigger up to four
external devices even if the floodlights themselves are set to come on at
dusk and go off at dawn.

Independent of the setting of the THIS UNIT switch, and independent of any
signals sent to remote units upon detection of motion, the detector can
trigger up to four remote units on at dusk and off again at dawn. These
remote units are the four units that are +5, +6, +7 and +8 from the unit
number of the detector. Thus if the detector is UNIT 1, at dusk it will
send X10 signals to turn any or all of (individually selectable) UNITs 6,
7, 8 and 9 ON for the same house code at dusk and OFF again at dawn,
according to the sensitivity set on the DUSK control. As a second example
of the unit codes, if the detector is UNIT 14, then an or all of UNITS 3,
4, 5, and 6 for the same house code can be triggered to be on only during
hours of darkness. To reiterate, the detector can turn on up to four
remote units during darkness even if the floodlights themselves are set to
come on only when the detector detects motion.

The external units triggered by motion cannot be the same as those
triggered by dusk/dawn. Also if the DUSK control is adjusted to the
minimum to detect motion even during the day, the detector will not be
usable for switching lights on and off at sundown and sunup. In this
case, the attached floodlights will come on during the day, either
continuously if THIS UNIT is set to DUSK, or whenever motion is detected if
set to SENSOR.

One typical application would be to have the detector overlooking a back
door or patio. At dusk, the detector would turn on the front exterior
lights and some interior ones to make the empty house look lived-in. When
the detector detects motion in the back yard, it would turn on the attached
floodlights, other interior lights and a recording of vicious dog. These
would go off after the set time. Late in the evening, some sort of X10
timer would turn off the lights that came on at dusk, to simulate the
occupants going to bed.

Q119. How do I control an X10 device from a standard light switch?

The simplest situation is where you have a standard wall switch that
controls a standard wall outlet (sometimes only half of a split outlet).
This is common in newer homes where a switch by the bedroom door controls
an outlet for a light at the bed, or a switch at the living room entrance
controls an outlet for a floor or table lamp.

For the simplest case, you'll need an AC adaptor that puts out a DC or AC
voltage in the range 6-18 VDC, and an POWERFLASH INTERFACE (X10:PF284,
RS:61-2687). Plug AC adaptor into controlled wall outlet. Plug the
POWERFLASH INTERFACE into an adjacent wall outlet that is continuously on
(may be the other half of the split outlet). Connect the output of the AC
adaptor to the input of the POWERFLASH INTERFACE, select input mode 3 and
select which unit you wish to control with the dial on the POWERFLASH

When you turn on the wall switch, a voltage will be produced by the AC
adaptor and trigger the POWERFLASH INTERFACE to send the X10 ON command to
the selected unit. When you turn off the wall switch, this will cut
current to the AC adaptor and the POWERFLASH INTERFACE will send the OFF
command to the selected unit.

The not-so-simple situation is where your wall switch controls a light
fixture. In this case, you would have to hard wire the above components
into place, or install a split power outlet half controlled by the switch
and plug them in.

Q120. How do I control my garage door with X10?

Stanley makes a Light Maker garage door opener that receives and sends
X10-like signals which don't seem to be too compatible with standard
X10. There have been reports of a jammed door flooding the power line
with these signals and so jamming the X10 channel.

A standard electric garage door opener is actuated by a simple contact
closure. This can be triggered by an X10 event using the UNIVERSAL LOW
VOLTAGE MODULE (X10:UM506, LEV:6337, RS:61-2688) in momentary mode
connected to the existing garage door control contacts, possibly in
parallel with the existing manual switch. When the selected X10 command is
received (unit ON) from whatever controller, either wired or wireless, the
contacts are closed and the door opens or closes.

A more sophisticated control system could be set up using two UNIVERSAL LOW
VOLTAGE MODULEs and some means of detecting whether the door is already
open or closed. This could be simple magnetic reed switches on the door,
or signals from the motor controller (it knows when to stop opening or
closing the door). The idea is to accept only signals from one UNIVERSAL LOW
VOLTAGE MODULE when the door is open, and from the other only when the door
is closed. This would mean a different command (e.g. "1 ON") to open the
door, and to close the door (e.g. "2 ON").

A further "improvement" would be to connect an AC adaptor so it is powered
by the light socket or light circuit on the garage door opener, and
connect it to a POWERFLASH INTERFACE (X10:PF284, RS:61-2687). This would
have the lights in the garage (or anywhere else in the house) on when the
door is open. See details in Q119.

Using a wireless transmitter such as WIRELESS TRANSMITTER (X10:RT504,
LEV:6313, RS:61-2560) to control the garage door might seem like a good
idea. However, it's not very secure. Anyone with a similar transmitter
and the right unit and house codes (256 possible combinations) could open
your door. Many conventional garage door openers have a thousand or more
different codes from which you can choose.

Q121. How do I improve the accuracy of my CP290 Home Control Interface?

The CP290 Home Control Interface, for reasons unknown to mortal man,
does not take its clock timing from the power line to which it is always
connected except during power outages. It uses an internal crystal
oscillator which is generally not particularly accurate. Errors of a
several minutes per week have been reported. This is particularly
annoying for a device that is supposed to perform time control of

One approach is to replace the crystal with a higher tolerance one. The
procedure to do this is in Q511.

For those not inclined to brandish a soldering iron, the trick is to update
the CP290 clock regularly from a more accurate source. This could be done
manually using a wristwatch; most CP290 software provides a means to set
the internal clock manually. A bit better method would be automatically
from the computer to which the CP290 is connected; the internal computer
clock is usually more accurate (or more easily controlled) than the clock
in the CP290.

The software details for setting the CP290 clock are in Section 4 of this
FAQ. A simple utility could be written to synchronize the clock of the
CP290 with the clock of the computer every time the computer was turned on
(e.g. include in computer startup command file). Note for best accuracy
and consistency, the CP290 clock should be updated at the minute plus zero
seconds (i.e. exactly on the minute).

Q122. How do I make an X10 light brighten up from zero intensity?

Many people come up with the "requirement" to have an X10 light start from
zero intensity (off) and ramp up to some level of brightness, to simulate
sunrise, to avoid waking them up when they go to the bathroom etc.

The standard X10 incandescent dimmers (e.g. DIMMING FIXTURE MODULE
LEV:6376 or LAMP MODULE X10:LM465) cannot go to a absolute level of
brightness other than off or on. If the device is off and it receives
DIM commands, it will come on to full brightness and then start to dim
(i.e. relative rather than absolute) until it receives no more DIM
commands. If it dims right down to the point where the light it controls
is actually off, then it can be brightened up again manually to some
intermediate level. However if the device gets an OFF command (from an
ALL OFF perhaps) in the meantime, there is no way to set it to anything
less than full brightness without it first coming on at full brightness
and then dimming down.

Powerline Control Systems (see Q105) manufactures a line of X10 devices
that are much more flexible than the traditional (and inexpensive) ones
that are widely used. One feature of their incandescent control devices
is that they can start at zero brightness and go to any of 200 discrete
levels of brightness. They can also go directly to a pre-set brightness
level. Traditional X10 controllers may not be able to control these
settings, however.

Q123. What components are available for me to build my own X10 modules?

1. PIC Home Automation Library written by Ed Cheung. Note this is PIC
assembly code! Send email to Ed at if you
would like a copy. Also available at the FAQ ftp site, see

  "In my effort to move my Home Automation system to a distributed
  processing system, I have invested some time into programming the
  line of microprocessors from Microchip (the PICs).  I have decided to
  see if there is any interest in the library, and release it as shareware.

  "The library that I have created is interrupt driven and has the following
  modules: X-10 (using a TW523), IR (Sony SIRCS), LCD display, Analog to
  Digital (I use the P16C71), RS232, RS422, and RS485.  The interrupt
  driven nature allows the main program to set variables and initiate
  transmission.  The background processes will send the data out at the
  right time and rate.  In this manner, each chip can also receive several
  types of serial data at once (receive RS232 byte and X-10 at the same time).

  "I intend to have my computational nodes be compatible (but not identical)
  to HCSII's protocol.  AFAIK that is 9600 baud RS485 in a master-slave
  configuration (nodes speak only when they are spoken to).

2. BASIC Stamp II

Q124: What patents cover the X10 system?

These are US patent numbers.

    4 - 189 - 713
    4 - 200 - 862
    4 - 628 - 440
    4 - 638 - 299
    5 - 005 - 187

More patent information from David Buckley

X-10 Patents - The story so far...

There are four patents directly covering X-10, each of which appears
in a number of forms for the varying requirements of the given
patent authority.  All patents are assigned to Pico Electronics
Limited, of Scotland, in the United Kingdom.

The First and Main X-10 Patent:

This covers most of the essential features of X-10 as we know it.
It's all there, 120Khz pulses, timing, sending commands twice (more
accurately, 'at least once'), including little things like dimming
commands, and ultrasonic remote control.  This latter feature is
probably because Pico Electronics also have a patent on ultrasonic
remotes, using PWM technology.

David Chester Campbell, David Richard Thompson.
UK: Filed as 19428/77, Abandoned
UK: 1592971, filed 7Jan77, pub 15Jul81
US: 4,200,862, filed 28Dec77, pub 29Apr80
De: 2800472

The Second Patent:

This patent has a sketch of a US style (decora?) wall plate with 4
rocker 'buttons' on it.  It knows how to handle two or more buttons
pressed together.

The concept of 'collision detection' is added, i.e., it listens to
the mains to ensure it doesn't transmit when someone else is already
doing so.

Also, this patent covers 'multiple unit addressing' from one button

Finally, the concept of transmitting the carrier bursts over the
full half cycle is covered, as an aid to more reliable operation
particularly in multi-phase scenarios.

There is also a disclaimer to a number of the claims of the US
version of patent filed (gazette 15May88), but despite intensive
searching, I couldn't find it!

US: 4,628,440, Filed 12Nov85, pub 9Dec86
UK: Filed as 81/32173, withdrawn, replaced by EP.
EP: 0078,171, Filed 25Oct82, Pub 7Jan88

The Repeater Patent:

This covers regenerating X-10 commands across phases and separate
electrical systems.  It also amplifies (ugh!) on the earlier
statement that commands are sent twice, rather than 'at least once'.

Author: David C Campbell
US: 4,638,299, Filed 28Mar83, Pub 20Jan87
UK: Filed as 82/10198, withdrawn.
EP: 0,091,290, Filed 31Mar83, Pub 19Nov87

The Better Receiver Patent:

Most early X-10 designed used an analogue method of 120Khz tone
detection.  This patent suggests using digital techniques,
implemented in software, to extract the tone.  This stuff will be
familiar to any DSP gurus, and the maths is well above me.  Claim is
for improved performance in poor signal and high noise environments.

US: 5,005,187, filed: 23Mar89, Pub 24Apr91.

Other things bumped into during research:

UK 1535834 and 1535835, US 3,911,415:  All from Westinghouse.  X-10
differentiates itself from these patents, which are all to do with
reading electricity meters remotely etc.  Filed 26Jan76, pub

US 4,418,333 - This is the first useful input from WWW searches,
covers the concept of the remembered light level in a remote control
system.  Donald J Yusko, assigned to Pittway Corp, pub 29Nov83.

US 43,777,754 - Also from a web search, and despite the number
looking wrong, it's what it said.  Covers the quick "off on off"
flick to change an appliance from the off state to on.  Another one
from Pico Electronics.  Filed 26Feb81, pub 22Mar83.

Note: I didn't see the words 'Powerhouse' or 'X10' during any of the

Q125. What radio frequencies do X10 componants use?

Control remotes and security use 310 Mhz. Powermid uses 410 Mhz.

Q126. Where did X10 come from? (by Neil Duffy)

Pico electronics was (and is?) a small design house in Glenrothes, Fife,
Scotland. Its founders were originally employed by General Instruments
in Glenrothes but broke away to form Pico Electronics. Their first
designs were among the first of the electronic calculator chips. Chips
designed by Pico and manufactured by GI appeared in the calculators of
many manufacturers.

A second venture following on from the calculators was a track selecting
record deck in which an led/ photodiode pair was used to detect the
spaces between tracks on an LP. The usere could play the tracks in any
order, rather like the facilities that CD players provide today. This
project was given the internal code name X9 but eventually became the
ADC Accutrack. The Accutrack originally had an ultrasonic remote control
which transmitted bursts of 40khz. It repeated the code in blocks of two
words, one of the words if I remember rightly being the inverse of the
other. The receiver compared the two before accepting the command.

The next project was given the internal code name of X10 following on
from X9 and was never renamed. The original X10 units used a similar
design to the ultrasonic remote control of the Accutrack.

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