Look on the back of your existing remote and see what frequency printed on it. If it is 315MHz frequency then you can use this 382 Digital Remote as a replacement.
Marantec has used four different frequencies over the years so it's important you get the correct one (universal remotes don't work with Marantec operators). If you don't have a Marantec remote or if it has worn off the back then you'll need to pull the receiver out of the slot it's in and read the frequency printed on it. The radio receiver can be found in a slot on top of the powerhead (motor unit). The receiver is gray, 2-1/2"x1-1/2" and has a 12" long gray antenna wire coming out of it. Pull the receiver out of the slot and you'll be able to read the frequency on it. Don't forget to put the receiver back when you're done.