CEBus

CEBus, short for Consumer Electronic bus, also known as EIA-600, is a set of electrical standards and communication protocols for electronic devices to transmit commands and data. It is suitable for devices in households and offices to use, and might be useful for utility interface and light industrial applications.

History

In 1984, members of the Electronic Industries Alliance (EIA) identified a need for standards that included more capability than the defacto home automation standard X10. X10 provided blind transmission of the commands ON, OFF, DIM, BRIGHT, ALL LIGHTS ON, and ALL UNITS OFF over powerline carrier, and later infrared and short range radio mediums. Over a six year period, engineers representing international companies met on a regular basis and developed a proposed standard. They called this standard CEBus (pronounced "see bus"). The CEBus standard was released in September 1992.

CEBus is an open architecture set of specification documents which define protocols for products to communicate through power line wire, low voltage twisted pair wire, coax, infrared, RF, and fiber optics.

Technology

Powerline carrier

The CEBus standard includes such things as spread spectrum modulation on the power line. Spread spectrum involves starting a modulation at one frequency, and altering the frequency during its cycle. The CEBus power line standard begins each burst at 100 kHz, and increases linearly to 400 kHz during a 100 microsecond duration. Both the bursts (referred to as "superior" state) and the absence of burst (referred to as the "inferior" state) create similar digits, so a pause in between is not necessary.

A digit 1 is created by an inferior or superior state that lasts 100 microseconds, and a digit 0 is created by an inferior or superior state that lasts 200 microseconds. Consequently, the transmission rate is variable, depending upon how many of the characters are one and how many are zero; the average rate is about 7,500 bits per second. A 400 microsecond burst is an end of frame indicator and also saves time. For example, if the 32-bit destination address field has some of its most significant bits zero, they need not be sent; the end of frame delimits the field and all receiving devices assume the untransmitted bits are zero.

CEBus transmissions are strings or packets of data that also vary in length, depending upon how much data is included. Some packets can be hundreds of bits in length. The minimum packet size is 64 bits, which at an average rate of 7,500 bits per second, will take about 1/117th of a second to be transmitted and received.

Other media

Other media besides powerline carrier are specified: coaxial cable, infrared, radio frequency, and optical fiber. The initial offerings supported only a powerline carrier.

Addresses

The CEBus standard involves device addresses that are set in hardware at the factory, and include 4 billion possibilities. The standard also offers a defined language of many object oriented controls which include commands such as volume up, fast forward, rewind, pause, skip, and temperature up or down 1 degree.

Manufacturers

Presently, all of the communications hardware, language, and protocol is available on a chip produced by Intellon Corporation in Ocala, Florida and by Domosys Corporation in Quebec City, Quebec, Canada. Intellon or Domosys sell the chip to other manufacturers for use in their products, and offer to manufacture private label and OEM products using the CEBus standard. Intellon and Domosys also sell developer kits to develop a CEBus compatible product.

Having moved out of the laboratory and into the market, the CEBus trademark is owned by the EIA. Ongoing developments are conducted by a group known as the CIC (CEBus Industry Council). The CIC is a non-profit organization made up of the representatives of many national and international electronics firms, such as Microsoft, IBM, Compaq Computer Corp, AT&T Bell Labs, Honeywell, Panasonic, Sony, Thomson Consumer Electronics, Leviton, and Pacific Gas & Electric. Anyone can become a member of the CIC by paying an annual fee of $300 to $10,000 and fulfilling certain other requirements.

Although there is no restriction from anyone using the CEBus standard, the CIC is developing a non-profit testing laboratory which will be funded by certification charges. Manufacturers are encouraged to use the testing laboratory to verify the conformance of their product and its performance in a home network environment. When the performance is certified, the manufacturer pays a certification fee and is licensed to include the CEBus logo on their product.

See also

• Electronic Industries Alliance
• C-Bus, a similar protocol with similar applications, but lacking a powerline carrier option, used mostly in Australia