an external output unit configured to output {HEAD ~ a signal} of {TAIL ~ contents} including an image to said second wearable display, and 
of
an external output unit configured to output { HEAD ~ a signal } of { TAIL ~ contents } including an image to said second wearable display , and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH