detecting, by the implantable device, failure to receive {HEAD ~ a response communication} from the external device within {TAIL ~ a specified maximum response time value} 
within
detecting , by the implantable device , failure to receive { HEAD ~ a response communication } from the external device within { TAIL ~ a specified maximum response time value }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL