X-10 is the technology that enables controllers like HAL to send and receive signals over standard home power lines. Using the X-10 protocol, HAL can communicate with any electrical outlet in the home.
X-10 receivers come in several forms. They may be as simple as a lamp module that plugs into an electrical outlet or an X-10 receiver outlet that replaces a standard outlet. You can control overhead lights by replacing the existing light switch with an X-10 receiver switch. X-10 receivers are available from home automation resellers.
X-10 differentiates devices by the address assigned to each device. The address is made up of a House code and a Unit code. The house code is a letter between A and P. The unit code is a number between 1 and 16. For instance, a lamp module set to a house code of B and a unit code of 14 is said to have an address of B14. There are a total of 256 unique addresses that can be created.
An X-10 sensor in HAL can respond to any device that has the ability to send an X-10 signal when it's activated. For instance, suppose a motion sensor is programmed to send an X-10 signal of F-05 "on". Within HALdeluxe and HAL2000, you could create a sensor called "Outdoor Motion Sensor" and specify that it will receive an X-10 signal of F-05 "on". When that motion sensor is activated (senses movement) it sends an X-10 signal throughout the house. When HAL receives the signal it recognizes the F-05 address and acts accordingly. The sensor could also be used to trigger a Rule.