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