An APG as it is said in the other post, is an input output device that allow the switching system to send or receive information to or from a remote destination. These information could be the configuration dump of the MSC, BSC, etc.. could be Statistic, CDR, counter etc….
the info are collected at a speed of 100 Mbit/s (APG c/2) or 1Gbit/s (APG C/4 ) thanks to ethernet links.
The APG is in fact two node (A and B) that form a cluster.each node is embedded with windows 2003
Hope it will help