The user monitor module 20 is a portable device that may include a transmitter capable of emitting {HEAD ~ one or more kinds} of {TAIL ~ signals} and a receiver capable of receiving an external signal 
The user monitor module 20 is a portable device that may include a transmitter capable of emitting { HEAD ~ one or more kinds } of { TAIL ~ signals } and a receiver capable of receiving an external signal
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH