Is it possible to configure NM-4B-S/T ISDN BRI Module on an ISR router for my connection to the PSTN for voice? Or do i need to use the VIC one?
Sadly the NM-4B-S/T does "not" support voice.
Voice Hardware Compatibility Matrix (Cisco 17/26/28/36/37/38xx, VG200, Catalyst 4500/4000, Catalyst 6xxx)
Hope this helps!