Hi again and thanks for that information.
OK - that is a relatively old phone system - perhaps 3-4 generations from the current technology. So it COULD be that the system has simply "worn out" and has a failure of some of the "features" of the system.
OR - This could be a service provider issue, as sometimes not being able to see the Caller ID is because the service provider is having issues SENDING the Caller ID information through the phone lines.
To find out which of these is the issue, we must TEST the Uniden system AND the phone line by one (or more) of the following methods:
1) Swap in a DIFFERENT Caller ID phone for the Uniden system, and see if that different phone works properly (do you have a Caller ID phone that you can bring with you on your next visit?).
1a) (ALTERNATE TEST) RESET the Uniden phone system - to see if the system STARTS to work - after the reset.
You can RESET the phone by removing the battery from the handset, removing the power adapter from the BASE unit, and removing the phone cord from the base unit. Leave ALL disconnected for 15 minutes, then reconnect the power, phone line, and battery and TEST (have someone place a test call and check the Caller ID).
2) Take the Uniden system to a DIFFERENT location (neighbor or friend's home - with working Caller ID service) and connect it there - to see if the Caller ID now works (at the different location)
If you find that the issue IS the Uniden system (does not work at another location), I would recommend replacing the system with a newer generation system that suits your Grandmother.
This may be a good opportunity to "take her shopping" - if she is able and enjoys that - OR - simply do a little "online shopping" and show her what is available that way (bring printouts if there is no internet access near her home).
A good place to start looking is Amazon, and I have a couple of links below that can get you started.
NOTE: Look for the systems that do NOT include a built-in answering system for lower cost systems.
Click Here --> Uniden cordless phone one handset (search results)
Click Here --> Panasonic cordless phone one handset (search results)
NOTE: Uniden and Panasonic are both "top quality" systems that I recommend.
Please let me know the results of your TESTING and what is found - when you can. And please let me know if you have any more questions.
If this has answered your question(s), please take a moment to rate MY service level (Excellent is my goal) so that I get credit for my time helping you with this question.
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Thanks, ***** *****