What dimming technologies are supported by Clipsal C-Bus?


10 March 2022

What dimming technologies are supported by USA Clipsal C-Bus?

Product Line:
Clipsal C-Bus Automation North America

Clipsal C-Bus
Commercial or Residential Installation
United States

When specifying C-Bus to control dimming, the Lighting System Designer/Engineer must specify the appropriate dimmers and light fixtures that are compatible with one another.


It is important to match the correct dimmer to the ballast and/or bulb in light dimming applications.  The different dimming technologies are not cross-compatible. 

Forward Phase Angle Dimming
Forward Phase Angle Dimming is the technology of C-Bus Pro Dimmer SLC5104RD5, SLC5102TD10 SLC5101TD20 and Phase Angle Dimmers SLC5504TD4A, SLC5504TD4AP, SLC5508TD2A, SLC5508TD2AP.  These types of dimmers are also known as Leading-Edge Dimmer, Standard Phase Dimmer, Triac Dimmer, and MLV Dimmer.   In Forward Phase angle dimming, the sine wave form is shut off for a portion of every half cycle (120 times per second)  after the AC voltage crosses the zero voltage line.  Resistive loads such as incandescent and tungsten halogen lamps work with this technology.  Low voltage ballasts that use a magnetic transformer (MLV) to create the lamp voltage (6, 12, 24V) as well as neon (cold-cathode) ballast will work with a forward-phase angle dimmer as well.   Some types of fluorescent dimming ballast and LED power supplies may operate with forward phase angle dimmers but it is strongly advised to check with the manufacturers of the ballast and lamp.

Forward Phase

Reverse Phase Angle Dimming
Reverse Phase Angle Dimming is also known as Trailing Edge Dimmer or ELV-Type Dimmer.   Like Forward Phase Angle technology, the sine wave is also cycled on/off every half cycle except that the voltage is energized after crossing zero.  This is opposite for Forward Dimming where the voltage is energized before crossing zero.   Reverse phase angle dimmers are often required on dimmable LED and 3-wire CFL fixtures using Electronic Low Voltage (ELV) solid state transformers.  Clipsal C-Bus in the United States does not support Reverse Phase Angle Dimming.

ELV Phase

0-10 VDC 
Some Light Fixture Dimmer Drivers require an analog 0-10 VDC control signal from which the fixture will references as a control input to its light fixture dimming circuit.   Clipsal C-Bus devices SLCLE5504TAMP or SLCLE5504HAMP can be used to send 0-10 VDC signals to these types of light fixtures.