A hard disk drive is placed within {HEAD ~ a cartridge} which includes {TAIL ~ a second printed circuit board} 
A hard disk drive is placed within { HEAD ~ a cartridge } which includes { TAIL ~ a second printed circuit board }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL