I am sometimes astonished at the thought processes that may (or may not) have gone into the design of some products.
Like the audio system in my car, which has a built-in Tom Tom satnav. There is only one power button for the system, which activates the radio, and the sat nav. When I'm driving, I don't want the radio on, and certainly not when I'm trying to listen to the lady who gives me directions.
So did it not occur to the designers, that not everyone wants to listen to the radio? Would it have killed them to put a power button on the satnav so that it can be used independently of the radio?
What you have to do is either adjust the volume of the systems somehow (haven't quite worked that one out yet, as there's only one volume adjust button!), or switch the radio to 'Aux' input, with nothing connected on that source.
Wow, just wow, that this got past probably several design reviews, and nobody thought that was less than ideal!