Linux to Unix problem

: hi. we have instaled a server Unix 5.0.4, running aplication in RMCOBOL 85. Getting access from linux Redhat 6.1, but it did not work the funtions keys F1 to F5 with any emulator (we have proved wiht VT100, ansi, VT220, wich one we get a better result of our requeriment was vt220d , but it reconigzed pushing the keys CTRL+A since CTRL+E respectly, we would like to know how do we have to do that the key funtions work correctly. The another thing is with the aplications screen cobols, we can not run aplication cobol and the sysadmsh with the same emulator, we just get the aplication screen in bad status and it does?nt work well (F1-F5).