Re: Hardware mute buttons which didn't mute
At a previous job the support and sales teams had headsets (sorry, cannot remember the brand but I'd recognise them if I ever saw them again) which had a headset which could be disconnected from the adapter box and a mute button on the headset adapter box that sat on the desk next to the phone (there were 3 controls on the box, can't remember what the other two did)
Plantronics had adapter box like that that plugged betwen handset and phone. If I recall correctly one button was to switch between headset and handset, one was mute, and one was volume control.