The present invention provides compounds of formula Iand pharmaceutically acceptable salts thereof. A management mode of operation of a processing blade of a blade server is activated. During normal operation the hold-down device moves over a first range of movement in response to changing swath thicknesses. The outer electrode conductor wire is electrically isolated from the inner electrode conductor wire, and may have either a single or double filar configuration. In this way, the pulse width modulation of the individual LED control signals is not cut off, or reduced in width by the group dimmer signal. A related method is also provided.