What is X10?

This system was originally offered by BSR, a company that made audio equipment. Over the years, the product line spun off into a separate company, the local manifestation of which is called "X10 USA".

The simplicity and utility of the X10 system caused numerous companies to join in on the fun. X10-compatible equipment has been marketed by G.E., Radio Shack (Plug-N-Power), Sears, Stanley (Lightmaker), IBM (Home Director), Zenith, and others.

How Does It Work?

The X10 protocol consists of a "unit number" and then a "command". For example, you can say "lamp #3", "turn on!" - and it happens. You can address several units before giving a command: "lamp #3", "lamp#12", "turn on!".

These commands are sent between "base stations" (transmitters) and "modules" (receivers). In order to make that lamp a part of the X10 system, you need a "lamp module". This is a plastic box smaller than a pack of cigarettes. You set a dial on the module to "number 3", plug the lamp into the module, then plug the module into the wall outlet. Then you turn the lamp's switch on and leave it on - you never need to touch it again, because the lamp can now be controlled from an X10 control panel anywhere in the house. You can have as many control panels as you want; the only one that is active is the one that you are currently pressing a button. You can also set more than one receiver module to the same unit number; they will all go on and off at once.

X10 makes a distinction between "lamp modules" and "appliance modules". Appliance modules are capable of handling larger loads, simply turning them on and off. If you wanted to turn on your coffee maker in the morning via X10, you would use an appliance module. Lamp modules aren't capable of running heavy loads, like heaters, motors, or fluorescent lamps. But they do offer the ability to turn on, off, and dim. In addition, lamp modules know that they are lamps. With a single X10 command from a "panic button", you can turn on every lamp module in the house - without starting the coffee maker.

Since the X10 signals travel along the power lines, you run the risk of accidentally sharing control signals with your neighbor. After all, he buys electricity from the power company, too. You don't want him to turn on your coffee maker in the middle of the night when he is just trying to water the lawn. Thus X10 includes in the protocol a "house code", represented as a letter A-P. X10 modules will only respond to control signals that carry the correct house code. Thus Mr. Barnabas can set all his X10 stuff to house=B and Mr. Jones can set his stuff to house=J, and the neighbors live in peace.

The X10 protocol allows for 16 house codes and 16 "unit codes" (module numbers). More than one module can share a unit code: a room with two fans might have them both set to house=B, unit=4. Then whenever you say "module 4", "turn on", you get air in the living room. If 16 unit codes is not enough, even with sharing unit codes, you might consider using more than one house code. I have so many X10 gadgets in the house that I assign a house code to each room.

Over the years, the X10 protocol has matured somewhat, adding new commands and bidirectional communication. There are now radio-based X10 devices. There are numerous computer interfaces to put your automated home in the care of your computer - providing true home automation. There have been at least two different models of telephone answering machine that allows you to control your house from afar. There have been several timers that send X10 signals, and at least one clock-radio. The line of X10-compatible equipment is growing all the time.

What Are the Tradeoffs?

• X10 equipment is inexpensive.
• It requires no special wiring.
• It is easy to set up and use.
• Systems can be small or large - you can start with just a couple of pieces and grow if you like it.
• X10 is easily placed under computer control.
• A radio-controlled version is available and very compatible with the rest of the system.

The following are drawbacks of X10 as a home automation system:

• X10 communication can be thwarted by other carrier-current devices, including wireless intercoms.
• X10 signals can be degraded, damped, or stopped by power-conditioning equipment, including inexpensive "noise-supressing" power strips, certain brands of computer power supplies, and my DAK bread maker. [There is a solution for this - a "choke".]
• There is no guarantee that an X10 command will get to its destination. If you send a command to turn off the heater, the command might get zapped by line noise and never have a chance to turn off the heater.
• The limitation of 16 house codes and 16 unit codes makes the address space a bit tight - there is no way to grow above 256 devices.
• Most houses are wired with two separate 110 circuits. X10 signals sent from a control panel plugged into one outlet might not get to the lamp module plugged into the outlet across the room - if it is on the other "leg" of the 110. [There is a solution of this - a "signal bridge".]
• It takes about a second to send an X10 command. While that command is being sent, you can't send another, or both commands will be lost.

A Gallery of X10 Equipment

The dark brown one in the upper left is from the early days of X10. You can tell from the thumbwheel switches on the sides used to set the house code and unit number. Newer modules use small rotary switches on the front that you need a screwdriver to set.

Note that many manufactures put their names on the front, but they are essentially identical inside.

Here is a collection of appliance modules, over time.

The dark brown one in the lower left is from the early days of X10. Again, note the thumbwheel switches on the sides. The big unit on the upper left is a heavy-duty model, suitable for air conditioners and the like.

Many manufactures put their names on the front, but they are essentially identical inside.

Lamp modules are available built into wall switches. When mounted in behind the switch plate, in place of a standard switch, you have X10 features without blocky modules sitting around. Like other lamp modules, these dim, too.

The one on the laft is ancient, and uses a toggle switch. Modern X10 wall switches feature a pushbutton. The unit on the right is a two-way switch. Above it is the remote switch. The two switches in the middle look similar from this angle, but they're not - the one to the left of middle is quite a bit thinner than the right of middle.

This is the Maxi Controller. It is capable of addressing all 16 units on the house code you set it to.

The top is protected by a smoked plastic cover that flips up.

I have two of these in the master bedroom, two in the living room, one in the kitchen, and one in the garage. The X10 people have made a lot of money off me over the years, but have made my life a lot easier.

These are Mini Controllers. They are capable of addressing only 8 units on the house code you set it to. Note the small slide switch, towards the bottom, in the middle. When the switch is towards the left, the control panel talks to devices 1-4. When you slide the switch to the right, it addressed units 5-8.

This is an older model of the mini controller. The discoloration on the upper left seems typical of this model when kept in service for years. Presumably, there's a component under that area that gets warm.

The red button on the right is an illuminated "panic" button that sends "all lights on".

I have one of these mounted on the wall in every bedroom.

This is a chime. As the name implies, it emits a pleasing sound when it is told to turn on via X10 signal.

I use several of these around the house to make my doorbell heard in the back rooms.

This is the chime being sold in 2005. [Wolfstone reader Alex Boyd referred me to this one.]

There are a lot of tricks you can do with X10. These appliance modules have been hacked. The one on the left is now momentary-activation. The one on the right has dry-contact output.

This is the powerflash transmitter. It is a special transmitter that is set for a particular house code and unit number. When activated, this unit turns on the target device. It is also able to send a stream of "all lights on" and "all units off" commands, flashing lights on and off. This feature is often handy for burgular alarms. [I forgot to take a picture of the powerflash. Wolfstone reader Alex Boyd referred me to this one.]

This transmitter has numerous options: it can be triggered by dry contacts or low voltage (6-18V AC, DC or Audio). It can activate the target device either as long as the input signal is present, or momentarily.

I have one of these hooked up to my doorbell. When the bell is rung, the powerflash activates chimes in the back room.

This is the "universal module", sometimes called "sounder/actuator module" or "relay module". When activated by X-10 signal, it can emit a beep noise and/or close dry contacts. It can work in momentary mode, or leave the contacts closed until you tell it to open them again.

The dry contacts can switch up to 5A at 24VDC. I use one on my fog machine!

Wireless X10 Equipment

Eventually, the X10 folks added a wireless form of X10 control. They did a good job of hooking the two together, so that wireless X10 controllers can activate standard carrier-current X10 modules.

This is the basic radio-control kit.

On the right are two versions of the hand-held remote control panel. They send signals to a special appliance module, on the left. It takes the radio signals and turns them into carrier-current signals that activate all standard X10 modules.

If it is a long distance between your transmitter and the receiver, you might need a radio repeater. It picks up signals from your hand-held remote control and retransmits it.

Now, this one's clever. It is an extremely inexpensive computer interface.

It works by hooking up to your computer's serial port. It then transmits radio signals to your radio receiver module, which pumps X10 signals into your wiring.

Where Can I Get This Stuff?

What if it doesn't work?

• Probably the most common complaint of beginning X10 users is that signals sent from a panel in one part of the house, are not heard in another part of the house. Sometimes you can send from one wall socket in a room and not pick up the signal from a socket just a few feet away. But the problem goes away when you turn on the electric stove.

  This happens because most homes are wired with two separate sets of wiring, and one socket is on one "leg" and the other socket is on the other. This is dramatic and obvious when sockets from each leg are present in the same room - you ask yourself "why can't the signal go from one side of the room to the other?" The problem is a bit more subtle when you try to send from a socket on one leg in the bedroom to a socket on the other leg in the living room. When this fails, the beginning X10 user is likely to write it off as a distance problem.

  These are all signs that you need a "signal bridge". The signal bridge takes whatever X10 signals it sees on one leg and lets them pass to the other. Signal bridges are relatively inexpensive. You can even make your own with a capacitor.

• If your neighbor's X10 equipment interferes with yours, you need a "signal block" to keep his signals out of the power coming into your house. Signal blocks tend to be expensive, and must be installed at your main fuse panel by a professional electrician.

• Certain appliances in your home can generate signals that interfere with X10, or just "short out" X10 signals. This usually requires that you locate the offending device and put a "noise filter" on it.

  A common offender here is the "wireless intercom" that sends voice signals through the power line. Filtering those is not an option - if it can't send signals into the power wiring, it can't get its job done. And if it does, it interferes with the X10. If you are lucky, this will only happen when the intercom is actively transmitting.

What about power strips and extension cords?

Power strips come in at least three flavors, and some of them do cause trouble for X10.

• Plain-vanilla power strips just have a plug on one end and sockets on the other. They might have a switch and an indicator light, but nothing that processes the power that it conducts. This kind of power strip presents no problem at all to X10 signals.

• Power strips with just surge protection also do not hinder X10. The protection is usually done with one or more MOVs, or perhaps a special gas-discharge tube. You can tell them by the claims on the box - the surge protection is a "feature", and they can only charge you more for it if they tell you about it.

• Power strips with "noise protection" or ones that claim to "reduce interference" do cause problems with X10.

  The cheapest way to do provide some noise control is to throw a cheap capacitor across the line. This will not only disrupt signals flowing through the power strip (from a transmitter in the bedroom to a receiver plugged in to the strip), but will also cause problems for any X10 device plugged in anywhere on the same leg of the 110. This one can be hard to diagnose, when a signal from the bedroom to the living room no longer gets through because you put a power strip on the computer in the den.

  More expensive noise filtering schemes axist, using multiple capacitors and coils. They, too, are likely to cause trouble for X10 operation.