tailieunhanh - Apress - Smart Home Automation with Linux (2010)- P10

Apress - Smart Home Automation with Linux (2010)- P10:Linux users can now control their homes remotely! Are you a Linux user who has ever wanted to turn on the lights in your house, or open and close the curtains, while away on holiday? Want to be able to play the same music in every room, controlled from your laptop or mobile phone? Do you want to do these things without an expensive off-the-shelf kit | CHAPTER 1 APPLIANCE CONTROL C-Bus Although there are several well-known protocols for appliance control X10 is the best known by a long shot with members of the general public being aware of it primarily because of its low barrier to entry. Within the HA community however it is the ownership of a Clipsal C-Bus system which becomes the About C-Bus The C-Bus system was developed by an Australian company Clipsal as a means of controlling various light systems remotely. Clipsal s original intention wasn t in the field of HA but in stadium lighting rigs and commercial arena and conference centers. This meant the system had to support much longer cable runs than would be utilized in a home setup and a larger address space. It succeeded on both counts with cable lengths of 1km being possible with 100 appliances on a subnet with each subnet being capable of connections to another six through basic bridges or considerably more through the now available Ethernet bridges. Differences Between X10 and C-Bus C-Bus s primary difference is with its installation. Although X10 transmits its data along existing power cables C-Bus devices are controlled by utilizing a proprietary protocol that travels along a separate Cat-5 cable. Consequently such installations can be carried out only by qualified Clipsal-approved staff pushing up the initial cost. However once all the cables have been laid one achieves the benefit of a near-zero level of maintenance since the interconnects will always exist and remain future-proof. It also provides two-way communication between the switch and a computer making it trivial to query the state of the light dimmer or appliance. Furthermore since the signal speed is not limited by the zerocrossings in the power line all light changes happen instantaneously a benefit that only those with many years of experience with X10 systems can truly appreciate. To lower this initial overhead Clipsal has recently introduced a wireless version of C-Bus which .