For the 800, 840/840i or 880i
This helpful square on the CapTel display screen lets you know when there are sounds on the line (such as the other person speaking) even if the sound is not loud enough for you to hear. If you see that the signal meter has stopped flickering, it means the other person is done talking. Even when the other person has finished, you may s till be waiting for captions. It is helpful to say something like “hang on a second” or “one moment please” to give yourself a little time t o finish reading the captions.
For the 2400i
The signal meter in the lower right of your phone shows when there is sound coming over the line, even if the sound is not loud enough to hear. The more sound wave coming out of the handset, the louder the sound.