This is coming back to me because I ran into it in a new customer's in January. They had an old TVS-50 and it has something to do with message waiting notification and it's option 2. You have to turn it on at every extension. I think it's log in, dial 5 2 and turn it on. I don't have my 50 manual with me (and you have to have the CD because it's not on the Pana website anymore) but it was something obscure and simple.

Carl