Hello, You can use the number keys for navigation. You would need a DTMF decoder,so that each specific key press can give some sort of navigation. For more info #-Link-Snipped-#

Vortex Flow is also the working principle of cyclone separators.

Also we can use VFD's (variable frequency drives) to increase or decrease the RPM by varying the frequency. Synchronous speed=120*f/p f=frequency p=number of poles of the motor.