In a conventional system, all remote devices must be connected individually to a central controller unit. This involves the use of many, maybe hundreds, of cables and can be very complicated and expensive to install. But a communication bus system carries information from all remote devices to a central controller unit in a single cable, making it convenient to install into any type of building and at a fraction of the cost of installing a conventional system.

Example: Hotel with 75 rooms, each room having:

• Lock (2 wires)
• Aircon-control (2 wires)
  
• Key access control (4 wires)
  
• Panic and service button (4 wires)
  
• Smoke detector (4 wires)
  
• Intruder detector (4 wires)

With normal wiring:

Every device needs to be connected with 1 cable to the control unit, so about 6 cables per room are required, with lengths up to hundreds of meters. So our example hotel would require 450 cables for 75 rooms.

Disadvantages:

• Expensive
  
• Requires a lot of space and many cables per room
  
• A lot of work to install
  
• Requires many large plastic pipes between rooms and control unit
  
• Requires many inputs at the control unit or extra input/output modules
  
• Fixed, not flexible, impossible to add extra features later
  
• Confusing for the installer to understand and separate the cables

With bus wiring:

Every device is connected to a small control unit inside the room. This control unit is connected to the power supply (2 wires) and the communication bus (2 wires).
The communication bus connects to every room. No need to make a separate connection between every room and the control unit.

Advantages:

• Less expensive
• Requires only 1 cable (4 wires) going to every room
• Easy and quick to install
• Requires only 1 pipe and cable between control unit and rooms
• Requires no inputs at the control unit
• Flexible, easy to add extra features later
• Easy for the installer to understand

So now our example hotel would require only one communication bus cable for all rooms

Conclusion

Installing a communication bus into large buildings makes economic sense as it is more cost-effective and easier to maintain. There is also the possibility of adding further devices at a later stage without causing major disruption.

See also our Wired? page for more information on the bus system.