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222 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

BACnet/IPv6, Master-Slave/Token-Passing over RS-485, ZigBee and LonTalk. There is no
common configuration tool and the majority of those available are not open source. It was
designed primarily for large buildings and communication between buildings. The scale
and nature of BACnet mean that it is not directly relevant to the smart home market in the
context of this chapter.
Twisted pair networks have been the focus for much of the development of intelligent
control systems, as they provide the performance, robustness and redundancy required.
However, there are a number of other transport media available that also need to be con-
sidered. Most of the systems just described have developed protocols for a number of
these media, including powerline, radio frequency, fibre optic and IP.
Powerline Technologies

The use of the mains electrical network to transmit data by superimposing low-energy
information has been used since the very early days of the mains electrical system. Initially,
it was used primarily to transmit information between power stations and substations
to assist in demand and fault management, although there are examples of consumer
devices such as baby monitors dating back to the 1940s. The clear advantage of powerline
systems, especially in the domestic market, is that the infrastructure is already in place.
Many attempts have been made to address the limitations associated with this method,
such as interference, speed and security (Erbes, 2008).
X10
The X10 system was the first general-purpose home automation system and remains pop-
ular today as a low-cost option. Launched in the United States in 1978, it was designed
to send control signals over the mains wiring, sending relatively simple unidirectional
commands via a 16-channel command console to a lamp module and appliance module,
which were soon joined by a timer module. 2
The system response using this method is slow, and commands sent simultaneously
can interfere leading to lost commands. The company has been responsible for some
interesting innovations over the years and the system has evolved, including incorporat-
ing bidirectionality, but it remains a low-cost and simple system.
CEBus
CEBus is a standard intended purely for the US market. It was intended primarily to
increase the range of commands available for powerline-based systems, although it is
an open system applicable to many media, and was an attempt to open up the high-end
market to powerline systems. The protocol is available on a chip produced by Intellon
Corporation in the United States and Domosys Corporation in Canada. It uses four layers
of the OSI model and includes commands including feature and functionality discovery
and enumeration.

2 https://www.hometoys.com/content.php?url=/htinews/oct99/articles/rye/rye.htm.