Adding a COM4 You can add one COM4  to KSU1  and  one COM4  to  the KSU2.   These modules  expand  the  DX-80 system  CO  line  interface  capacity to a  maximum of eight  CO line  ports in each KSU  (16 total CO line ports when used in KSU 1 &  2). When  adding  a COM4 to  either KSU,  connect to  the  408M/E  via the COM4  module ribbon  cable.  This ribbon cable has the logical system  address  of SLOT 5  in both cabinet 1 (KSU1-408M) and cabinet  2 (KSU2-408E).   COM4 modules are  installed using  four  1.5 cm brass-color standoffs.   Always install  the COM4  module beneath the  CPM  module (in KSU1) by first  removing the CPM, installing the  COM4,  and then re-installing the CPM.  This is required whenever  you install  the InSkin Voice  Processor.