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X-10

X-10 is a communications protocol that allows compatible home networking products to talk to each other via the existing electrical wiring in the home. Basic X-10 powerline technology is almost 20 years old and was initially developed to integrate with low-cost lighting and appliance control devices. X-10 originally started out as unidirectional only; however, capability has recently been added for bidirectional communication if needed. Nevertheless, the vast majority of X-10 communication remains unidirectional.

X-10 controllers send signals over existing AC wiring to receiver modules. The X-10 modules are adapters that connect to outlets and control simple devices. X-10 powerline technology transmits binary data using an amplitude modulation (AM) technique. To differentiate the symbols, the carrier uses the zero-voltage crossing point of the 60 Hz AC sine wave on the cycle's positive or negative transition. The zero-crossing point usually has the least noise and interference from other devices on the powerline. Synchronized receivers accept the carrier at each zero-crossing point. To reduce errors, X-10 requires two zero crossings to transmit either a zero or a one. Therefore, every bit requires a full 60 hertz cycle and thus the X-10 transmission rate is limited to only 60 bps. A complete X-10 command consists of two packets with a 3-cycle gap between each packet. Each packet contains two identical messages of 11 bits (or 11 cycles) each. Therefore, a complete X-10 command consumes 47 cycles that yields a transmission time of about .8 seconds. Using X-10 it is possible to control lights and virtually any other electrical device from anywhere in the house with no additional wiring. The X-10 technology and resource forum designs, develops, manufactures, and markets products that are based on this standard. Today, scores of manufacturers make X-10-compatible products that, at $10 to $30, scarcely cost more than their incompatible counterparts; according to the X-10 group, more than 100 million such products have been sold. These home automation products are called "powerline carrier" (PLC) devices and are often installed by builders who want to offer home automation as an additional selling feature. The home automation line consists of "controllers" that automatically send signals over existing electric power wiring to receiver "modules," which in turn control lights, appliances, heating and air conditioning units, etc. With the X-10 standard, you can literally walk into a nearby electronics store and purchase all of the necessary equipment to automate your home with the X-10 standard. The main disadvantage for legacy X-10 technology is that it has very limited capability in terms of both speed and intelligence. It is a technology relegated to control applications only because of its low data rate and rudimentary functionality.


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