DigiTalk-mono is a font meant for KDE 4.x's clock, to give the 'digital' appearance of KDE 3's kicker clock.
KDE 4.x should provide 'shadow effect' for it! to make it look exactly like KDE 3's kicker clock.
HOW TO INSTALL:
1. extract the font digitalk-mono.ttf say in your home folder
2. right-click on the digitalk-mono.ttf -> (choose) actions-> install...
3. personal or system (your choice)
4. restart plasma-desktop; "killall -TERM plasma-desktop; plasma-desktop" or logout and logon back
5. right-click on the digital-clock in the panel, choose -> digital clock settings
6. choose 'digitalk-mono' in drop-down menu of font-style
7. set custom color (black) for better visibility.
8. click ok,
and there's your beautiful digital clock!