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