mp interfaces ------12 ea. variable V11/V24/V28/V35 ISDN DTE/DCE interface, line speeds up to 1.75 Mbps.
mp12 interfaces----12 ea. variable V11/V24/V28/V35/ G.703/ ISDN DTE/DCE interface, line speeds up to 2.3 Mbps.
mpr interfaces -----12 ea. variable V11/V24/V28/V35/ G.703/ DTE/DCE interface, line speeds up to 2.3 Mbps.