X10 is a communications "language" that allows compatible products to talk to each other via the existing 110V electrical wiring in the home. No rewiring is necessary. Up to 256 different addresses are available. If you want more than one device to respond to the same signal, simply set them to the same addresses. All X10 compatible products can be freely mixed and matched - Use Leviton together with X10 [http://www.x10.com], Stanley�, etc.  

There are 3 basic types of devices:
   * Transmitter
   * Receiver
   * Transmitter/Receiver Combo
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Why its there a page related to X10 on the Tcl Wiki?  

[MPJ] Because most computer control of X10 devices are done with serial communication and Tcl is a great language for serial port communication.  There are also RF devices that are used to interface with X10 devices.  These are used for remote control of X10 receivers.  These RF remotes also have other purposes that I will describe below (soon).
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'''TRANSMITTERS'''

[X10-CM17A] A Serial Port connector that transmits an RF signal to a RF/X10 convertor

'''RF REMOTES'''