AT&T System 25 - Manual (Page 45)

Last Number Dialed
You can redial the last number you dialed (up to 16 digits) by
using the b u t t o n .
Numbers are stored in when you use the Speed
Dialing feature or the following buttons:
Numbers are not stored in when you use the
Account Code Entry or Call Accountability features or the
following buttons:
Using Last Number
1 Listen for dial tone.
2 Press
NOTE: If you dialed the last telephone number with any of
the following buttons, you must use the same type of button
to obtain dial tone before you redial: