[Elecraft] KX3 KXUSB vs KXSER interface

[Bruce Beford]

I would think that whatever external keying device you are using would have
to connect via the KEY jack. This would be a contact closure (or the
equivalent) to ground, with the KEY jack in straight key mode, via the KX3
menu.73,
Bruce, N1RX

> After KXUSB terminates in a 3.5mm plug, there is no place for DTR line. 
> Then how is arranged the CW keying by a computer?

> 73, Val LZ1VB