Panasonic KX-TD7890 Reference Manual page 7

c
About
the
RESET
Button:
If
the
unit
stops operating properly even
after set
it
up
correctly, press
RESET
on
the
bottom
of
the
base
unit
with a pointed
object,
such
as a pen,
etc.
Pressing
RESET
does
not erase
any
stored
telephone
numbers
(p.
13).
7