First, {HEAD ~ the video signals} pass through the video operational amplifier and video buffer 312 and {TAIL ~ the video switch circuit} 306 
pass through
First , { HEAD ~ the video signals } pass through the video operational amplifier and video buffer 312 and { TAIL ~ the video switch circuit } 306
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH