{HEAD ~ The apparatus} further includes a switching network for coupling the door speaker and microphone to a local telephone set and {TAIL ~ a remote telephone} set selectively in any combination 
includes
{ HEAD ~ The apparatus } further includes a switching network for coupling the door speaker and microphone to a local telephone set and { TAIL ~ a remote telephone } set selectively in any combination
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH