With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
isdnSigStatsInConnected
isdn Sig Stats In Connected
1.3.6.1.2.1.10.20.1.3.3.1.2
The number of incoming calls on this interface which were actually connected.
Back to ISDN-MIB MIB page.
IPHost Network monitor allows you to monitor isdnSigStatsInConnected on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco firewalls right now.