Comment 10 for bug 258630

Just toggle the master in your gnome volume control down to zero.

You will still get sound out of docking station but not of internal speaker. The master volume control does not control the docking station headphone jack.

What I think why Dell designs the hardware like this:

1. Both, the analogue and digital sound output of the docking station are having the same source. This source is activated by the iec958 switch.

2. The digital sound output has no way to detect if a cable is plugged in or not. So if activated by iec958 there's a signal on the digital output. It doesn't matter if a cable is plugged or not.

3. Combine 1. with 2. The analogue output of the docking station is activated at same time with digital output. So this jack does not recognize if a cable is plugged in or not. It's just activated by iec958.

4. The digital output does not have a volume control. The volume control is done by the amplifier.

So if my suggestions are right there's a reason why you have to activate the iec958 switch and toggle down the master.

But to understand why such a hardware design should be clever and smart you have to ask Dell. I do not know.