elements in the key and in {HEAD ~ the lock} which prevent the lock from changing from the locked condition to the unlocked condition when the key is not connected to the lock and which permit {TAIL ~ the lock} to change from the locked condition to the unlocked condition when the key is connected to the lock, 
permit
elements in the key and in { HEAD ~ the lock } which prevent the lock from changing from the locked condition to the unlocked condition when the key is not connected to the lock and which permit { TAIL ~ the lock } to change from the locked condition to the unlocked condition when the key is connected to the lock ,
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH