See also:

Tachometer
The tachometer displays the engine speed in revolutions per minute (rpm). ...

Federal Communications Commission (FCC) Rules and with Industry Canada Standards
See Radio Frequency Statement   for information regarding Part 15 of the Federal Communications Commission (FCC) Rules and with Industry Canada Standards RSS-GEN/210/220/310. ...

Volume Control
VOL/ (Volume/Power): Turn clockwise or counterclockwise to increase or decrease the volume. ...