X10 is the name of a company, a set of protocols designed by that company,
and the products they make and sell (as do other companies) based on those
protocols. These devices and protocols are used to remotely control
devices (modules) with no wires directly between them.
Three media are used:
- Digital data sent over household wiring: DC pulses are
superimposed on the AC signal at the zero-crossing points of the sine
wave. This is what most people refer to when they talk about X10. This
will generally work thoughout a house, but noisy motors, curge
supressors/UPS's, and faulty wiring can degrade the signal.
- RF (radio) signals: An analog RF signal is sent
through the air. Moderate range, pretty reliable.
- IR signals: A digital infrared light signal is sent
through the air. Shorter range, very reliable.
All of these media use one-way transmission. The controlled device does
not send a signal back to the controller acknowledging the signal or
confirming that action was taken (there is a new breed of devices that
do, but they are the exception).
Each controlled module is identified by a house code (letters A to P) and
a unit code (numbers 1 to 16) for a total of 256 codes. More than one
module can have the same code. All modules can respond to ON and OFF
commands. Lamp modules can also respond to DIM commands, ALL LIGHTS ON,
and ALL LIGHTS OFF commands. Most controllers can only control one house
code at a time, and most only control the first 8 unit codes.
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