System Diagram
Figure 1 diagrams the overall system for the simplest X-10 application, remote control of a device. Instead of the typical circuit in which the switch controls the power flowing to the lamp, the switch signals an X-10 transmitter. That transmitter sends a message to the X-10 receiver using signals over the power lines. The receiver detects the signals, decodes the message, and controls the power flow to the lamp according to the content of the message. Messages can command the lamp to be on, off, or dimmed to a specified level.
FIGURE 1: Simplest X-10 system diagram
The standard ISO seven-layer communications model (Figure 2) describes any communication system, and so applies to X-10 systems.We’ll start with the physical layer and work upwards. X-10 systems don’t implement layers three (networking) through five (session), so we’ll skip directly from the link layer to the presentation layer.
FIGURE 2: ISO seven-layer model
Application: Specifies interactions among applications
Presentation: Controls information formatting for display or print, and data encryption
Session: Monitors and brokers communication between systems, including security,
logging, and administrative functions
Transport: Supports end-to-end movement of data between systems, and ensures error-free
transmissions through error checking and correction or retransmission
Network: Routes data between systems across the network to ensure data arrives at
the correct destination
Data Link: Defines the rules for sending and receiving information from one computer
to another
Physical: Implements the physical transfer of information between computers
Our discussion starts with the physical layer, showing how information physically moves from one device to another.