Panasonic KX-TG5571M Operating Instructions Manual page 82

Useful Information
Power failure
Problem
The unit will not function.
82
For assistance, please visit http://www.panasonic.com/consumersupport
Cause & solution
L This product is not designed to make calls in the event
of a power failure. We recommend connecting a
standard telephone to the same telephone line in the
event that emergency calls need to be made during a
power failure (page 11).