As I stated above, it's an EXTENSION cord, not a longer dock cable (there is no longer dock cable available). You connect the male end of the USB extension cord to the AC adapter, and connect the male end of your 3' dock cable to the female end of the USB extension cord.
Or, just get an AC extension cord. Or a powered USB hub for your desk. Or, just unplug the iPhone - it has a battery. Or, use a Bluetooth headset (which is what I do) - then you can get up and walk around.
So many options... 🙂