How to clear all registrations from the base

Suggest you reset handset and register again with base.

Instructions from manual...
Resetting Handsets If you have trouble with a handset or if you want to replace one, clear the registration information from the base and the handset: 1. Press & hold END and # at the same time until you see the System Reset menu. 2.If you still have the base the handset is registered to, select Deregister HS, then select the handset you want to reset. If you don't have that base anymore, select Base Unavailable. 3. To confirm, select Yes. The handset displays Handset not registered. Registering Handsets If you see a "not registered" message on a handset, you must register it to a base before using it. 1. Place the handset in the base; the display should say Handset Registering. 2.Wait until the display says Registration Complete (about 30 seconds), then pick up the handset and press TALK/FLASH. 3.If you don't hear a dial tone or the display says Registration Failed, charge the battery completely, then try again.

You might try to de-register the handset and re-register
it to the base. Be sure the handset's battery is well
charged, a weak battery can impede the registration.

( I ) To de-register the errant handset:

1. Press and hold the [END] and [ # ] keys at the same time until the screen displays
"System Reset, Deregister Handset"
2. press [select]
3. scroll to "Base Unavailable"
4. press [select]
5. display says "Not Registered"

( II ) To register the handset to the base:

1. open the base display's [menu]
2. scroll to "Register Accy."
3. press [select]
4. on the handset, press and hold [ # ] until
the handset display says "Registering"
5. In ~30 seconds, handset display will say
"Registration Complete" or
"Registration Failed".

This is described on page 22 of the manual.
A free copy of the User's Manual can be obtained
at www.manualslib.com .

Good luck!
------------

This sounds like Handset #1 has lost its "registration" with
the base. De-registering & re-registering is often easy.

First, be sure the handset battery is well charged as a
weak battery will interfere with the registration process.
Then try this ( 'works for the D1680, D1481, & similar):

To deregister the handset:

1. Press and hold the [END] and [ # ] keys at the same time,
after a few seconds the display will say
"System Reset, Deregister Handset"
press [SELECT]
scroll to "Base Unavailable"
press [SELECT] (chirps) press [END]
display reads "Place in base..."

Next, to re-register the handset:

2. Set the handset into the base cradle and wait,
within ~30 seconds the handset should display
a "Handset #" and be good to go.

Good luck!
--------------

This sounds like the handset has lost its "registration" with
the base. De-registering & re-registering is often easy.

First, be sure the handset battery is well charged as a
weak battery will interfere with the registration process.
Then try this ( 'works for the D1680, D1481, & similar):

To deregister the handset:

1. Press and hold the [END] and [ # ] keys at the same time,
after a few seconds the display will say
"System Reset, Deregister Handset"
press [SELECT]
scroll to "Base Unavailable"
press [SELECT] (chirps) press [END]
display reads "Place in base..."

Next, to re-register the handset:

2. Set the handset into the base cradle and wait,
within ~30 seconds the handset should display
a "Handset #" and be good to go...

Good luck!
--------------

All of the handsets appear to have lost their
registration to the base and will need to
be first de-registered then re-registered.
It may be necessary to do this in three stages.
First be sure that all of the handset batteries
are fully charged.
1.
Clear one of the handsets of its registration:
hold down both the [END] and [#] keys
at the same time until the display shows the
SYSTEM RESET menu.
Since the handset is not recognized by its
base, select "Base Not Available".
Confirm the choice by selecting "Yes".
This handset will now display
"Handset Not Registered"
--
2.
With "...Not Registered" displayed, place
the handset into the base unit cradle.
The handset should now dieplay
"Handset Registering"
After ~30 seconds the display should show
"Registration Complete" and will have a
handset unit number.
If the unit shows "Handset 1" (doubtful)
then just repeat steps 1 & 2 above for each
additional handset in turn. This can also be
the route if you do not care what the numbers
are and do not exceed the maximum count
for your system ( some are 4, 5, or even 12 ).
If the handset is a number other than 1 you
may want to clear the base & re-register
all of the handsets:
3.
Using the now-registered and working handset
(number x), press both the [END] and [#] keys at the same time until the display shows the
SYSTEM RESET menu.
This time, choose "Deregister HS" and the
System Reset Menu will prompt you to
select from the list of registered handsets
which one you want to deregister: choose
one that is NOT the one you have working.
Cycle around deleting them all until only the
one that is working is left: select that one and
the system will be ready to start re-registering
all handsets again from Handset #1.
Start at process (1) above, then (2).
Good Luck!!
===============================

The "END" and "#" key combination can be used for several purposes:

1) If wanting to use an ALREADY REGISTERED HANDSET on an alternate base, and if if the INITIAL BASE isn't available to deregister the handset:

1a) Press "END" + "#" until it for 5+ seconds (wait for it to beep)
1b) Choose the "Base Unavailable" option
1c) That'll deregister the CURRENT HANDSET so that it can be re-registered on ANY base.

2) If a BASE has a handset registered to it which you no longer want registered but the registered handset is missing or broken:

2a) Grab another WORKING handset which is properly REGISTERED to the BASE in question
2b) Press and hold the "END" + "#" key for 5+ seconds (wait for it to beep)
2c) Choose the "Deregister HS" menu option
2d) Pick the REGISTERED HANDSET # to de-register. (Every other registered handset EXCEPT THE ONE YOU'RE ON will appear in the list!)

Same manual as lethean provided on a similar post but Page 24 if the previously used Base is Unavailable and your phone shows "Deregistration" in the Menu.

Base Unavailable (Handset Only)
To clear the base registration data in the handset, please follow these steps:
Press and hold [] and [#] for more than 5 seconds. Select the BASE UNAVAILABLE submenu.
BASE UNAVAILABLE appears. Move the cursor to select YES, and then press the OK soft key.
ARE YOU SURE? appears. Move the cursor to select YES. Press the OK soft key.

OU might need to deregister the hand set first by holding down the red end (hang up key) and keep it down while holding the # key. If deregister wont work use base unavailable and yes, you are sure twice.

List the handset numbers of those working handsets
Using a WORKING handset follow these directions
Resetting Handsets
If you want to register the handset to a different base or
replace a handset with another one, you must first clear the
registration information from the base and the handset.
1. Press and hold [ ] and [#] for
at least 5 seconds, until the
SYSTEM RESET menu
appears.
2. Select the DEREGISTER HS
submenu. WHICH HANDSET?
appears in the display.
3. Move the cursor to select the handset ID to be de-registered
from the list, and then press the OK soft key. DEREGISTER HS
appears. CHOSE A NUMBER THAT IS NOT ONE OF YOUR WORKING HANDSETS
4. Move the cursor to select YES, and then press the OK soft key.
When ARE YOU SURE? appears, select YES. You will hear a
confirmation tone.
PUT THE HANDSET IN THE BASE CHARGER AND IT SHOULD REGISTER

Hope This Helps - It worked for me

YOU might need to deregister the hand set first by holding down the red end (hang up key) and keep it down while holding the # key. If deregister wont work use base unavailable and yes, you are sure twice.

List the handset numbers of those working handsets
Using a WORKING handset follow these directions
Resetting Handsets
If you want to register the handset to a different base or
replace a handset with another one, you must first clear the
registration information from the base and the handset.
1. Press and hold [ ] and [#] for
at least 5 seconds, until the
SYSTEM RESET menu
appears.
2. Select the DEREGISTER HS
submenu. WHICH HANDSET?
appears in the display.
3. Move the cursor to select the handset ID to be de-registered
from the list, and then press the OK soft key. DEREGISTER HS
appears. CHOSE A NUMBER THAT IS NOT ONE OF YOUR WORKING HANDSETS
4. Move the cursor to select YES, and then press the OK soft key.
When ARE YOU SURE? appears, select YES. You will hear a
confirmation tone.
PUT THE HANDSET IN THE BASE CHARGER AND IT SHOULD REGISTER

Hope This Helps - It worked for me

On the Base Station select HS Registration then on the Handset hold # for 2 sec