In {TAIL ~ the process}, a series of pulses are produced, dependent upon {HEAD ~ the rotational speed} of each drive 
In { TAIL ~ the process } , a series of pulses are produced , dependent upon { HEAD ~ the rotational speed } of each drive
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH