The loop of an analog line is left open during an onhook state, so the router doesn't know when anything is connected. You can use test commands to send ringing voltage to the other side, but the other side would need to go offhook for the vg224 to know a device was there.
You can increase the call history timer and then grep 'sh call history voice brief' for the string '2/[0-9]*' and throw it through 'uniq' for a listing of unique ports with recent activity after letting it sit for some time:
dial-control-mib retain-timer 1200
dial-control-mib max 35791
If this is SCCP or MGCP, you can leverage CM configuration to see what ports have extensions assigned, or look at CDR for the device to leverage what ports are active.
