tup, tun, dug, dus

Wherever possible in Elektor circuits, transistors and diodes are simply marked `TUP` (Transistor, Universal PNP), `TUN` (Transistor, Universal NPN), `DUG` (Diode, Universal Ger- manium) or `DUS` (Diode, Universal Silicon). ~ This indicates that a large group of similar devices can be used, provided they meet the minimum specifications listed in tables 1a and 1b.