I just got off the phone with TST concerning this lost signal/contact between sensor and monitor..
they said
1. the monitor cycles thru all tire positions constantly
2. after 20 minutes of attempting to contact a particular sensor
the last shown tire pressure & temp display will go way for that sensor
the monitor will issue a short chirp sound, not the alarm sound
so, its 20 minutes, not an hour
and there is a physical and audible indication that contact has been lost (for each such sensor)
they recommend the range extender for FW 35 ft or longer.