The FS44M has LED's for on footswitch indication of current active feature. This footswitch is for the current V3 with internal reverb and back lighting and the Legacy 3 heads.
The FS44M footswitch uses momentary switches and is not compatible with other amp series.
Please call if you have any questions about choosing the right footswitch compatible with your Carvin amp.”
Earlier versions of the V3 head without internal reverb or back lighting can not use this footswitch.