I'm a K2 user, and there are separate logic lines for dits and dahs. I believe the K1 uses a single logic line, with different voltages. The two-diodes-pulling-both-lines-down won't work. Please, some K1er correcct me if I'm wrong. Dan / WG4S / K2 #2456 <snip>I would like to pigtail a female 1/8 plug receptacle to a keyer interface on the LPT port, maybe bridged with a diode.</snip>