Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble, Carl.
This symptom usually indicates a hardware failure in the base station. We most often see this type of damage to the base unit as the result of a power surge, either through the phone or power lines. This is a very old system though, so it wouldn't be surprising to see a hardware fault just as the result of normal age related wear and tear.
The one thing you may attempt yourself is to fully reset the system:1) unplug both power and phone lines from the main base.2) remove batteries from all handsets3) wait at least 15 minutes, then restore all4) place a handset on the main base for a minute, as if to charge5) check for functionality.
Let me know the results, and I'll advise further if needed.