{HEAD ~ Each one} of the drive gears constantly meshes with its counterpart member of {TAIL ~ the driven gears} 
{ HEAD ~ Each one } of the drive gears constantly meshes with its counterpart member of { TAIL ~ the driven gears }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL