Clipsal C-Bus Specifications download pdf (Page 52)

C-BUS TRAINING MANUAL - VOL 1

2.1 Operation of Input Units

Any network needs to have input and output capabilities. Therefore, input units are a fundamental

building block of a C-Bus system.

Input units can only broadcast three types of commands on a C-Bus network. These are:

• on commands

• off commands

• ramp to (level) commands.

When a button is pressed on a wall switch, a message is sent across the C-Bus network for an output

unit to perform one of the three functions above.

An input unit can also perform timing functions. A press of a button starts a timer, and a command

is sent to an associated output unit. After a programmed time interval (of up to 18 hours), another

command is sent to cancel the previous (depending on the unit’s programming).

One of the main features of C-Bus (and the reason the system is so effective), is its self-checking

ability. At regular intervals an input unit issues a request over the network for a status report. In

response to this request, output units with the same Application Address broadcast their status

in the form of an MMI*. This allows inputs assigned to the same Group Address to compare and

synchronise their status. If the comparison disagrees, the input unit may take corrective action. This

corrective action could be as simple as updating its own indicator to match the status of the output,

or issuing a command for the output unit to change its state.

NOTE *MMI (Multipoint to Multipoint Interrogation).

2.2 Pressing a Button

If you press a button on a wall switch, one or more messages may be transmitted over the C-Bus

network. The message transmitted depends on:

• how the unit is programmed

• how long you pressed the button.

A change in ambient lighting, temperature level or the detection of infrared energy may be used

instead of a physical button press, to trigger a response in some input units. Such units include light

level sensors, temperature sensors and PIR occupancy sensors.

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Clipsal C-Bus Specifications Page 52