NIM-2FXS/4FXOP= Cisco 2-Port FXS/FXS-E/DID and 4-Port FXO Network Interface
4000 Series Router NIM-4FXSP Analog Voice 4 Port Network Interface Module - FXS, FXS-E And DID - Buy 4000 Series Router NIM-4FXSP Analog Voice 4 Port Network Interface Module - FXS, FXS-E
CISCO NIM-4FXSP 4-Port Network Interface Expansion Module for 4000 Series Router
Analog Voice Network Interface Modules for Cisco 4000 Series ISRs Data Sheet - Cisco
CISCO NIM-4FXS - 4-Port Network Interface Module - FXS. FXS-E and D