The coupler preferably comprises {TAIL ~ a compliant belt and pulley drive}, a worm and gear drive, or {HEAD ~ a bevel gear drive} 
The coupler preferably comprises { TAIL ~ a compliant belt and pulley drive } , a worm and gear drive , or { HEAD ~ a bevel gear drive }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD