New Exercise for the Group

Describe how the tire pressure monitor system works. On my 2006 LS430
Ultra model there are no monitoring devices present in the tire valve
stems. There are no monitoring devices evident to the tire guys who
install the tires. If you press and hold the tire pressure monitor
button under the dash, a light comes on and says pressure monitoring
is initializing - you drive it around for a block or so over 19 miles/
hour and the light goes out.

Extra credit - is the spare tire also monitored?