Handsets won't register - locked in one state

I had this exact problem on a D1780 and solved it by un-registering all of the handsets and then re-registering them. Before I did that it would only allow six phones to be registered at a time.

October 10th, 2013 at 9:19 amPROBLEM:
After de-registering handset, handset displays [REGISTRATION FAILED; UNAVAILABLE] when trying to register handset.
This worked for my UNIDEN TRU-9480-2
SOLUTION:
1) Remove handset from base
2) Remove power cord from back of base
3) Press and hold the [find hs] button on base as you plug the power supply back in; the charge light should then be blinking.
4) Return handset to base and it should register
GOOD LUCK!! HOPE THIS HELPS!!

Silent Mode
You can silence the ringers on the base and all handsets for a specific period of time; the answering system answers any incoming calls without playing anything through the speaker.
With the phone in standby, press and hold # on any handset. The phone prompts you to select the number of hours (1 - 9 or Always On) that you want it to stay in silent mode.
To confirm, press # or just wait about 5 seconds. The phone turns on the answering system and displays Silent Mode On on each handset.After the selected number of hours, the phone automatically exits silent mode. To exit silent mode manually, press and hold # again.
If the phone is in silent mode and you turn off the answering system, the phone exits silent mode.
Multihandset Features To use the features in this section, you need at least 2 handsets.
Your base supports a total of 12 cordless handsets: the one that came with the base and up to 11 DCX160 accessory handsets.You must register accessory handsets to the base before using them. (Handsets that came packaged with the base are already registered.)Handsets that aren't registered display a Not Registered message. For registration instructions, see p. 18, or see the accessory handset manual.If a handset was ever registered to a base, you must reset it before it can register to a new base; see p. 18, or see the accessory handset manual.Conference Calling
When an outside call comes in, two handsets can join in a conference call with the outside caller.
To join a call that's already in progress, just press Talk/flash or SpeSpeSpeaker.To leave the conference call, hang up normally; the other handset remains connected to the call.

Reset the hand sets that are out of range by doing the following:

1) Press and hold END and # for at least five seconds.
2) Move the cursor to select Base Unavailable and then press Menu/Select.
3) Select the base which you want to de-register from, and then press Menu/Select. Base Unavailable appears.
4) Move the cursor to select Yes, and then press Menu/Select. You hear a confirmation tone,

(For DCX150 handsets)
5) Place the handset in the base cradle for about thirty seconds. Handset Registering will appear in the LCD.
6) When the handset has registered to the base, the LCD will display Registration complete then show the handset
ID number.
If the display shows Registration failed, repeat the process again.

(For DCX200 or DCX300 handsets)
5)Disconnect the base AC adapter. Then press and hold find while you reconnect the adapter. Keep holding
find until the charge LED starts to blink.
6)When charged, registered handsets display a handset ID number. Handsets that have not been registered display:
7) On the handset, press and hold # until the handset beeps and displays Handset Registering.
8) When the handset has registered to the base, the LCD will display Registration complete then show the handset
ID number.
If the display shows Registration failed, repeat the process again.



User Manual Available Here

A search of Uniden support only said to call 1-800-297-1023 with handset registration issues. The rep picked up quickly and walked me through the reset procedure. Here it is step-by-step:

1. Remove battery
2. Hold down the * and # buttons and reinsert battery. You should hear a long beep. If not retry. (This is a bit awkward but hold the handset upside down and it's workable)
3. Screen will be blank. Immediately press the right soft menu button.
4. Screen will report that EEPROM is clearing and then state EEPROM Clear Ok
5. Remove battery (yes again)
6. Reinsert battery (this time there's no need to hold down any buttons)
7. Handset will reboot with Welcome screen and then state that phone must be registered (this is the status a handset should be in from the factory)
8. Place handset on base and it will register as normal

Short answer:
No. This model of phone can only support 4 handsets. If you need more than that, you will need to have a second base unit.

Detailed answer:
One of my handsets went bad, and I just bought complete DCT748-4 package from a seller on eBay for a very good price. This set was used, but in very good condition. I didn't need the whole set - just one handset - but like I said, it was a good price. Anyway, I began by telling my old base unit to de-register handset #2 (the failed unit). However, I then found that I could not register the "new" handset with my old base unit because it was already registered to the "new" base unit. So, I first had to apply power to the "new" base unit and de-register the handsets. Then, I placed one of the "new" handsets onto my old base unit, and it said "Handset Registering ..." and registered just fine. Just for the fun of it, I placed one of the other spare handsets into my old base unit. It said "Hanset Registering ..." but then it beeped and said "Registration Failed." This is because I already had 4 handsets registered to my base, and the base can not handle a fifth handset.

Dear....Fixya Team,

I'm Soontaree. Thank you for your reply email. I would like to let you know i'm already solved this problem. I just have a look from the Uniden Manual so i just follow them detail like as below,

Thank you for your help i will contact to you later if i have anything problem.

Have a great day.
Soontaree



Registering DSS7905 Accessory Handsets
Your phone supports a total of ten (10) cordless handsets. Handset(s) supplied in the box with the phone base are
pre-registered at the factory. If you purchase an accessory handset, you need to register the handset before use.
Only one handset can be registered at a time. When charged, pre-registered handsets display a handset ID number.
Handsets that have not been registered display.

Before registering the DSS7905 accessory handset, the battery pack MUST be charged for 15-20 hours.
To register the DSS7905 handset:

Place the handset in the telephone base charging cradle to begin registration.
During the registration process, HANDSET REGISTERING will appear in the LCD. When REGISTRATION
COMPLETE. is displayed; the handset has been registered to the base. If REGISTRATION FAILED. appears,
please try these steps again. When you register an accessory handset to the base, the handset ID will be
assigned.

Note:
If an accessory handset has ever been registered to a base, you must reset the handset before you can
register it to a new base. See Resetting the Handsets on page 24.

One has to completely deregister all handset by pressing end and # keys together till complete de registration is shown on handset screen. if the de registration is not done as above stated method the hand set will not register will show connecting on hand set screen.

Registering Handsets to the Base
Whichever handset you choose to charge in the base is automatically
registered to the base. Any additional handsets must also be registered to
the base before you can use them.
Be sure both handsets are fully charged.
One at a time, place each handset in the base. The charge/in use LED on
the base begins to flash, indicating the base is registering the handset.
Wait for at least five seconds, then pick up the handset and press
[talk/flash]. If the display shows TALK, the handset is registered. If not,
place the handset in the base to try again.
Press [end] and continue with the next handset.
Note:
Once both handsets are registered, it doesn’t matter which
handset is placed in the base or the charger.
When you charge the handsets, Caller
ID summary screen and the name of
the handset appears.

This can be find from uniden website.
http://www.uniden.com/pdf/DXAI4588-2om.pdf

I just successfully registered 4 TCX905s with my TRU8865 base - it's documented in the TCX905 manual.

Be sure the handset you want to register is fully charged.

Remove the handset you want to register from its charger.

Now unplug the AC for the main base, hold down the 'find handset' key on the base and plug the AC in again, when it beeps, you can let go of that button.

Hold down the '#' on the handset you want to register, it will show 'Registering Handset...' and when it beeps, it's done - registered, you're good to go :)