In the default setup, PF1-PF4 keys of VT100 are emulated by "Num Lock", "/", "*" and "-" keys of numeric keypad. To emulate PF1-PF4 keys by F1-F4 keys of PC keyboard, edit the keyboard setup file KEYBOARD.CNF like the following (see also Keyboard setup file):
[Numeric keypad] PF1=59 PF2=60 PF3=61 PF4=62 ; Key codes for F1-F4 keys are 59-62. [X function keys] XF1=off XF2=off XF3=off XF4=off ; XF1-XF4 items should be disabled, because ; key codes 59-62 can not be used twice in the setup file.