Panasonic KX- TC1721B Operating Instructions Manual page 3

For Best Performance
Battery Charge
A rechargeable Ni-Cd battery
powers the handset. Charge the The battery
battery for about 4 hours before is beneath
initial use (p. 14). this cover.
Base Unit Location
Calls are transmitted between the base unit and the handset using wireless
radio waves. For maximum distance and noise-free operation, the
recommended base unit location is:
Raise the
antenna.