If you operating a mobile of any manufacturer you don't want to bring the huge operator's manual with you. And the radios have become very complex and complicated to say the least. Especially when you have two or more radios in your vehicle of different makes, now it becomes even more complicated. I have a number of these little guilds in the glove box of my truck. I operate HF and 2 m/70 cm plus HF, so there is no way I can remember what all the buttons do on each radio.