There are currently three classes of eMTB: Class 1, Class 2 and Class 3.
Class 1 eMTBs, like the Shuttle, do not feature throttles. Instead, Class 1 eMTBs are equipped with a battery and a drive unit that assists your own pedaling effort. That system only assists when you are pedaling. In addition, the system stops assisting the moment the bike reaches a speed of 20 miles per hour in the United States and 25 KM/H in Europe.
Class 2 eMTBs feature a throttle—in other words, Class 2 eMTBs can provide a power boost even when you aren’t pedaling. It’s a very different machine.
Class 3 eMTBs look and function similarly to Class 1—the difference is that the drive unit on a Class 3 eMTB disengages once the bike hits 28 miles per hour.  Class 3 eMTBs allow for higher speeds and are typically regulated like dirt bikes and other OHV’s (off-highway vehicles).