A propriatary Nortel Networks device that allows you to remotely access the Nortel Norstar that it is attached to, hence the name Remote Access Device. The fast part of the name derives from the fact that a eariler version of the RAD (the I-RAD) only had one speed setting, (9600 baud) the fastRAD has 2 speed settings (9600 and 19200 baud). Neither baud rate is particularly fast, but I doubt the Nortel slowRAD would garner much in the way of sales.
Once you program the fastRAD with a password (this must be done on-site) you can make changes to the Norstar's programming,(change the names of the phones, allow/deny line access, MAC work etc) so if you are the administrator of 50 Norstar systems across the country, you can use the RAD to program them all from the comfort of your desk.(note: each Norstar much have its own fastRAD).
There is one caveat
to using the fastRAD however. Even though it sounds like a glorified modem, it is a Nortel Networks
glorified modem, which means you need a Nortel software package called Norstar Remote Utilities to access the fastRAD.