Owner's Manual
Page 11
... Pull at bottom to the display during power interruptions. The warning flashes about two months before leaving home for backup power) if your thermostat was wired to run on AC power when installed. M29422 PRO TH3110D / TH3210D M29421 Batteries are optional (for more than a month. Replace batteries once a year, or before...
... Pull at bottom to the display during power interruptions. The warning flashes about two months before leaving home for backup power) if your thermostat was wired to run on AC power when installed. M29422 PRO TH3110D / TH3210D M29421 Batteries are optional (for more than a month. Replace batteries once a year, or before...