Cisco Fourth-Generation Multi-flex Trunk Voice/Clear-channel Data T1/E1 Module

Expansion module - T1/E1 x 4 - T-1/E-1 - for P/N: ISR4321-PM20, ISR4331-PM20, ISR4351-PM20, ISR4431-PM20, ISR4461-K9-CAP, ISR4461-PM20