If you already implemented central logging, and you have also a Voice Gateway in your network, it is very annoying, that your logs are filled with ISDN-6-CONNECT/DISCONNECT messages, like this:

335414: May 19 19:07:49 CEST: %ISDN-6-CONNECT: Interface Serial0/0/0:26 is now connected to xxx N/A
335415: May 19 19:07:51 CEST: %ISDN-6-DISCONNECT: Interface Serial0/0/0:26 disconnected from xxx , call lasted 2 seconds
335417: May 19 19:08:18 CEST: %ISDN-6-DISCONNECT: Interface Serial0/0/0:27 disconnected from xxx , call lasted 871 seconds
335418: May 19 19:08:20 CEST: %ISDN-6-CONNECT: Interface Serial0/0/0:30 is now connected to xxx N/

You have an option however, to filter out these type of log messages with Message discriminator. Read more