CM 5300 had its adapters in SAPI-1 (RMP-1), TNS (via APK and another cassette with IMP board), SMEP (min. 2 controllers - older four-board RJ MPP and newer single-board CM 5012, SM 50/40 (board RJ MPP), PC and others... In most cases, they were simple controllers based on 8255 except for SMEP.