In {HEAD ~ step} 510, {TAIL ~ a recording request} is generated at a first receiving unit 
In { HEAD ~ step } 510 , { TAIL ~ a recording request } is generated at a first receiving unit
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH