Strange situation, I have an extreamly low volume output at the earpiece, but only when there is someone on the other end of the line. For example, the "beeping" sound when increasing the volume by using the dial appears normal strength, but conversations are impossible. This unit was a second hand purchase to add to my existing unit. Which functions normally. I troubleshooted for a long time. De-registering, registering, swapping bases... no luck, same problem. When making a call, person at the other end is barely audible at max volume. Anyone else run into this problem?