a control device for enabling the apparatus to displace in {HEAD ~ an automatic way} from a rest position to {TAIL ~ the checking condition}, and vice versa 
a control device for enabling the apparatus to displace in { HEAD ~ an automatic way } from a rest position to { TAIL ~ the checking condition } , and vice versa
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH