When the 'Elf Windows' (yellow ellipse) checkbox is selected the Cosmac Elf control windows will be shown. Default this is the front panel and if configured also the hex keypad and led module:
To configure the hex keypad select 'Hex' as keyboard type (blue ellipse) and to configure the led module select the 'Led' (magenta ellipse) checkbox.
The front panel includes the IN button, switches, Q LED and TIL displays.
Emulation of the TIL displays and the LEDs can take a lot of PC CPU power so default these are only updated every 100 ms. This can be changed via the 'LEDs' field (green ellipse). When 0 ms (or nothing) is specified the TIL displays and LEDs will be updated in real time.
Two types of TIL displays can be show, TIL 311 or TIL 313, selected via the choice button 'TIL' (orange ellipse).