I have a UnidenDECT 6.0 with 4 handsets. Recently handset #4 seems to have lost connectivity with the master unit as I cannot make any calls or receive any calls from #4 handset. Instead, the display shows searching. How do I get it back synchronized with the master unit?

SOURCE: handset does not work

Your handset is no longer communicating with your base. Depending on your model, the solutions can be a couple of different options. If I could view pdf files on this computer I would look it up for you. But here is the link to the manual on Unidens website- http://www.uniden.com/pdf/TRU8865-2om.pdf

Nonetheless, give this a try. Power down your base, and pull the battery out of your handset. Plug the battery back in the handset and set the bad handset in the base cradle, and then power up the base. Wait about 30 seconds, then give the phone a try. If it still does not work, then you need to try to "re-register" the bad handset back to the base. Look in the manual under "registration" procedures. Hope my help fixes it for you. Good Luck, CG

SOURCE: Uniden DCT648 register phone problem

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

SOURCE: handset won't ring

You need to reset the main base and make sure the ringer volume is turned all the way up. Disconnect the power from the back of the main base, press and hold find hs key while reconnecting power until you hear long beep. Should reset base and handset.

SOURCE: CALLER ID ONLY SHOWS "INCOMING CALL"

I was using this site while trouble shooting this in the US...
If the customer has DSL with filters in the same system go back to the NID and Isolate the DSL,
test the caller id and call waiting caller id. If this works you have Data Bleed coming from the DSL.
Make sure there are not two sets of filters on the line. Tjis customer had a filter with the DSL modem.

Doing this we just fixed an on going problem for a field tech who was the second callout on a customer issue.

SOURCE: How to remove Uniden handset from base

The brillian people at Uniden don't feel it necessary to provide this type information in their manuals. You have to trial and error to find it, but what can you do. All you have to do to reset the base unit itself is to unplug the power, then while holding down the delete key, plug it back in. Hold the delete button down until you hear a beep, which indicates it has reset. Now you can readd handsets and they will start at 1.