The X-10 system uses a standardized protocol and command set to handle
a variety of home automation tasks. It relies on a power line carrier (PLC)
communication system that superimposes a higher-frequency (120KHz) amplitude
shift keyed (ASK) carrier on top of the 60Hz (or 50Hz) power line carrier.
X-10 controllers can be plugged in at any point in the house wiring
system. Commands from a controller are transmitted through the entire house-wiring
network, and are not limited to any particular branch of the circuit (a
phase coupler allows the signal to bridge the gap between the two 110V.
circuits that typically feed a house). A special blocking device can be
installed at the breaker panel to prevent the X-10 signals from exiting
the home system and being broadcast into other homes or apartments that
may share the same power system.
All X-10 receivers, or "modules" will receive any command sent by any
X-10 controller in the home wiring system, in that system. Some newer modules
can send as well as receive. For the purposes of this document, an X-10
module can be classified as an I/O interface device.
When a module receives a command, it checks the "address" attached to
the command to see if it is the intended recipient. If the command was
meant for a different module, the command is ignored. When the intended
module gets the command, it acts upon it accordingly, switching something
on or off, dimming a light, sending a different command to some other device,
X-10 commands are limited to a set of 16 commands, called the standard
function set. However, most modules recognize only a basic function set
of seven commands.
An extended code packet has also been developed to increase the number
of possible transmitted functions, which is useful for home automation
systems that control several types of subsystems, such as HVAC, security,
audio, etc. However, due to the nature of the X-10 technology, this slows
down the data transmission rate due to the increased number of AC cycles
required to carry the additional information.
Addresses in the code are described by a four-bit "house" code (letters
A-P) and a four-bit "unit" code (numbers 1-16), thus A-1, A-7, C-14, G-9,
To instruct one or more modules to carry out a function, house/unit
code message packets are transmitted to all of the modules for which the
command is intended. This "arms" the modules. Then, another message packet
is sent, with the desired function code. The armed modules carry out this
function. A module is "disarmed" by the first house/unit code message packet
received that does not match its house/unit code after a function code
is received, or by the reception of an "all off" function.
The two most common X-10 module types are lighting modules and appliance
modules. Lighting modules usually control resistive loads, such as incandescent
lights, and can switch the lights on or off or dim them down or up. Appliance
modules use a relay to switch the attached devices on or off.
X-10 controllers can be stand-alone plug-in devices, or can be hard
wired into a system. Some are simple, with only a few basic controls, while
others may have built-in timers, clocks, and telephone access capabilities.
The controllers generally have built-in buttons, dials, etc. to provide
the user interface to the system.
Other devices have been added to compliment the X-10 system, such as
radio frequency (RF) or infrared (IR) controllers and modules. These are
used to help cover situations not suited to power line carrier technology.
For example, a security system may use RF wireless door/window sensors.
A "base station" controller receives the RF command from the sensor, translates
it to an X-10 command, and then transmits it on the power line network.
Naturally, to extend the X-10 system's utility in this way adds cost and
complexity to the system, without any improvement in reliability, since
it still relies on the X-1 0 power line communications technology for network
Repeaters may be required in larger systems where signal attenuation
is a problem.
An X-10 system is low cost and usually easy to install, since most X-10
components use existing house wiring as the communication medium. However,
there are some drawbacks:
- It is subject to power line "noise" that can reduce the reliability of
- The wiring topology is often unknown, especially in older structures.
- Attenuation of power line control (PLC) signals on the power line network
is variable and often unpredictable, affecting the reliability of PLC transmission.
- Other technologies may also use the power line network for communications,
and may interfere with X-10 communications.
- It has a limited command set, compared with certain other technologies.
Data transmission rates are slow, limiting applications to situations where
response time is not critical and where high data throughput is not important.
- It requires at least one transmitter (controller) to superimpose or "inject"
the signal on the power line carrier, plus a separate receiver (system
interface device) for each controlled equipment item or circuit.
- Some low-end X-10 devices may have problems with data "collisions" during
New enhancements to the X-10 technology are improving the reliability of
the system, but it is still subject to problems. The performance of this
technology is more difficult to improve; it would require a substantial
increase in cost and complexity, which would defeat the purpose of the
X-10 system: a low-cost system that performs adequately well for many basic
home automation needs.
New X-10 "modules" are being developed all the time to handle a variety
of tasks. As mentioned, a module can be a transmitter, a receiver, or include
both transmitter and receiver. It can be designed to control specific types
of equipment. So, just what can a module do? Here is a partial list:
- Switch - Turn line-voltage devices, such as lamps, on and off.
- Dimmer/Speed Control - Directly dim lights or control motor speeds.
- TV/Audio VCR Controller - Send device-specific commands to other devices,
such as a TVs, VCRs, radio receivers, audio equipment, etc.
- Thermostat - X-10-compatible thermostat that can report temperatures.
- Sun sensor, temperature sensor, and wind sensor, shutter and drapery control.
- Telephone responder, etc.
Some major X-10 manufacturers include Honeywell, Leviton, Advanced Control
Technologies, IBM, and X-10 USA.
Back to Top
CEBus Network Architecture and Topology
The CEBus standard allows the use of a variety of network media, including:
- Twisted-Pair Wiring
- Coaxial Cables
- Infrared Signals
- RF (Radio Frequency) Signals
- Fiber Optic Cables
- Power Line Signals
- AV (Audio-Video) Bus
CEBus communications hardware, language, and protocol are available on
a chip made by Intellon Corporation in Ocala, Florida. Intellon sells the
chip to manufacturers for incorporation in their products. lntellon can
also manufacture private label/OEM CEBus products. Developer kits are available
CEBus home automation systems can be installed in existing dwellings,
using the original 110V. or 220V. household wiring for data exchange. While
this is not the optimum situation for rapid data throughput, such as for
video signals, it does provide additional flexibility where rewiring is
inconvenient or prohibitively expensive. IR or RF would typically be used
for remote control purposes. CEBus technology may be encapsulated within
individual appliances that connect to the power outlets, or within remote
control devices that plug into the outlets.
The CEBus standard includes such technologies as power-line spread spectrum
modulation. Spread spectrum starts modulation at one frequency and changes
the frequency during its cycle. It begins each burst at 100 KHz, linearly
increasing the frequency to 400 kHz over a 100-microsecond period. The
burst ("superior" state) and the absence of burst ("inferior" state) create
similar digits, so a pause interval is not required.
A digital 1 is created by an interior (or superior) state that lasts
100 microseconds. A digital 0 is created by an inferior or superior state
that lasts 200 microseconds. This means that the transmission rate will
vary, depending upon the number of 1s vs. 0s.
No matter what media is used, the CEBus control channel data is transmitted
at roughly 8,000 bits per second. Media can also carry data channels. Data
throughput will depend on the capabilities of the medium. CEBus control
messages are always of the same format, no matter what medium is used.
A message contains the address of the recipient, but does not include any
routing information, thus the recipient can be anywhere on the network,
on any medium.
The CEBus control channels carry commands and status messages. These
messages consist of strings or packets of data bytes that can vary in length,
depending upon how much data is in the message. Packets can be hundreds
of bits long. Minimum packet size is 64 bits, and each packet takes an
average of about 1/117 second to be transmitted and received.
There are commands for allocating data channels, but the majority of
the CEBus standard concerns the control channel specifications. Data channel
encoding is not specified in the CEBus standard.
Device addresses are set in hardware at the factory, and allow 4 billion
possibilities. CEBus also offers a defined language of object-oriented
controls, including commands such as volume up, fast forward, rewind, pause,
skip, temperature up or down 1 degree, etc.
Messages may be addressed to (sent to) a specific device, or a special
address may be used to reach all devices on a network or just a specified
group of devices. Addresses may be either individual or group addresses.
Devices may belong to more than one group. Note: Not all CEBus-compatible
devices support group addressing, and the number of groups a device may
support can vary. This varies by manufacturer and model.
CEBus topology allows devices to be placed anywhere on the network,
independent of the medium, as long as the device has the correct CEBus
interface for that medium. Messages being sent from one media type to another
are sent via a router circuit. The router may be a separate device, or
it may be integrated within an appliance.
Control messages are distributed among the CEBus devices and routers.
A centralized controller is not used for delivery management. No specific
topology is specified in the CEBus standard. All controlled device connection
points on a medium are treated logically as though they were on the same
bus. This means that all controlled devices on a particular medium sense
the arrival of a data packet simultaneously. All devices read the destination
address in the message, but only those with a matching address read the
rest of the contents of the message and react to them.
Audio-video requirements are available, but the Electronics Industry
Association (EIA) has not yet released specifications. It should describe
a cluster-controller bus, consisting of a thin cable with eight twisted-pair
wires. It is designed for interconnection of a cluster of home entertainment
products within a small area, typically one room. Maximum cable length
is 30 feet. The cable carries three audio channels, four video channels,
plus the CEBus control channel. A single connector is used to connect the
cable to a controlled device. In terms of fiber optics, the CEBus technical
requirements have been released, but specifications are still under development
by the EIA.
In terms of coaxial cables, CEBus specifies a dual-cable system. One
cable connects to in-home video sources (VCRs, cameras, etc.). The other
cable is used for distribution to any receivers in the system. At the head
end, any external video signals are combined with the signals from in-home
Back to Top
The Echelon system is based upon the existence of intelligent control devices
(nodes). In an Echelon system, also referred to as a "LonWorks" network,
communication between devices may be either peer-to-peer (distributed control)
or master-slave (centralized control). A common protocol is used for all
Whatever approach is used (centralized vs. distributed), each node has
a potentially high level of built-in intelligence. The nodes computational
capabilities allow processing functions to be distributed throughout the
system. For example, an Echelon-based temperature sensor can be intelligent,
performing programmed analysis of local temperature readings and filtering
the results so that only significant changes are reported to a central
controller or to other nodes. Control functions can also be distributed
throughout the system, providing better performance and reliability.
Nodes communicate with each other on a peer-to-peer basis using a common
protocol. Each node contains embedded intelligence that handles the protocol
and carries out processing and control functions. Each node also includes
an I/O interface that connects the node's micro-controller with the communications
network. On each node, most of these capabilities are provided by a single
chip, called the Neuron chip, which is available in several versions from
Motorola and Toshiba. The Echelon Lonworks technology is an open, but proprietary,
The Echelon approach does not use existing house wiring for communications.
While this requires additional wiring during installation, it eliminates
the problems and limitations associated with power line carrier (PCL) systems
like X-10. Transmission is much faster and more reliable, and is not subject
to power line interference, static, or changing line load conditions. In
addition, Echelon is not limited to any particular communications network
wiring/connection type. A variety of transceivers and connectivity products
are available. Gateways are available for Ethernet, Tl, X.25, Bitbus, Profibus,
CAN, Modnet, SINEC, Grayhill, Opto22 (digital), OptoMux, Modbus, ISA bus,
STD32 bus, PC/104 bus, VME bus, and EXM bus.
The built-in capabilities of the Neuron chip allow a tremendous range
of computation and intelligent functions to be carried out at the local
(node) level, but the Echelon LonWorks technology is not limited to node-level
processing; it also provides compatibility with host-based applications.
Host based applications are those that run on a processor other than one
of the processors in the Neuron chip. This could be a component microprocessor
that uses a Neuron chip as a communication coprocessor, or a Windows-based
PC that communicates with the system using a serial port or PC adapter
board. These applications allow the addition of servers, consoles, or monitors
to the system, and can provide centralized control for non-distributed
automation systems. They are also appropriate for migrating existing applications,
creating complex network management utilities, or building gateways to
A typical node in an Echelon system performs a simple task. Devices
such as proximity sensors, switches, dimmers, motion detectors, relays,
motor controllers, stepper motors, etc., may all be nodes on the network.
The interconnected set of communicating nodes performs the super-set of
complex control functions required for automating a home.
Smart House System
Appliance control signals, status information, and message data are carried
on the same channel and use the same protocol. The exceptions are video
signals and telephone data.
The basic topology consists of a star with branches that correspond
to the electrical branch circuits. At the star's hub is a System Controller,
which is typically placed in close proximity to the circuit breakers for
the home's electrical system. The System Controller includes an uninterruptible
power supply, surge suppressors, the telephone gateway, and the head end
for the coax cables. The System Controller handles the following tasks:
- System management.
- Routing of data to appliances.
- Scheduling for services.
The System Controller handles all message routing. Smart House has specified
a formal language for appliance control and status messages.
The Smart House system is based on three cable groups or types:
- Branch Cables - Power and digital data. Branch cables consist of a power
cable and a separate digital data cable (four twisted-pair sets). One twisted
pair is for data, another carries the system clock signal, and the other
two pairs are unused, or can be used for a separate branch.
- Applications Cables - DC power for sensors and digital data. Communications
Cables - Telephone wires and video coaxial cable.
Smart House wiring is best for new construction, since retrofitting would
involve substantial rewiring. Wall switches are not wired directly to outlets.
Rather, wall switches are connected to applications cables that include
a communications channel. When a switch is opened or closed, a signal is
sent to the System Controller, which acts according to a programmed table
to control various lights or outlets. This approach allows for relocation
of appliances, as well as switch reassignment, in which the same switch
might perform different functions, depending on the time of day or other
Smart House specifies a dual coaxial cable system. A downstream cable
carries video signals from sources such as cable TV, satellite dishes,
antennas, etc. An upstream cable carries video signals from internal sources,
such as CCTV, VCRs, computer terminals, etc. The head end in the Smart
House Service Center combines these upstream and downstream signals for
distribution on the downstream coaxial cable. This approach is similar
to the one used in the CEBus system.
The telephone gateway provides an intercom function and access to the
Smart House system for remote control operation. Specific ring patterns
indicate intercom calls from specific telephones in the home. The telephone
gateway includes a modem for remote control purposes. The touch-tone signals
from an external telephone can activate programmed data messages for operating
appliances or services in the home. A security code is required for access.
Synthesized voice instructions are available for remote control assistance.
Back to Top