I have found an excellent SS7 tutorial on the performance technologies website.
W/R to class 4 and 5 switches well you will have difficulty finding information as to the differences. Significantly a class 4 switch is used on trunk links only whilst a class 5 switch whereas class 5 access's subscriber lines and therefore has more functionality.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...