[Link: socketcom.com]They also make them with detachable dongles and in dual or quad configurations. I prefer the ruggedized, non-detachable type.
My trusty old quad model works fantastic on HTMs and the early Prontos. Can't tell you about the Yamaha though.
Have used them for years and years. Connect reliably and quickly to just about everything I've came across. GPS units, terminal servers, Tektronix/HP test gear, all kinds of central office and headend supervisory ports.
On the minus side, they cost a pretty penny.