OK, thanks Mitch and Mike. I've now gone back to a null modem cable and I've made some progress. I clipped D10 in the Remote RRC. That radio now powers up with the Control K3, the RRCs connect to each other and the Remote K3 delivers audio to the Control RRC. Hurray! The Remote K3 panel operates normally and it powers down with its own POWER switch. However, the Control K3 panel now goes catatonic whenever it is in TERM mode. The only controls that do anything are Long Hold MENU and POWER. Long Hold MENU toggles TERM/NORM mode. In NORM mode, the Control K3 operates normally but of course does not control the Remote K3. When I power down the Control K3, the Remote K3 stays on. Also, CW keying through the Control RRC does not work yet.
All this suggests to me that the connection is one way - with the exception of POWER on, nothing is flowing from the Control K3 to the Remote K3 although I do get audio from Remote to Control. I suspect the port assignments. They are identical on both RRCs but I have had trouble with the 2wire modem/router port forwarding assignments. The Admin pages are rather obscure. In particular, they don't associate a separate IP address with each application name. You associate a name with a port range and then assign it to an IP address but you can't then assign the same name to another IP address. So my port forwarding is set up for one but not both RRCs. This situation will go away when I move the Control RRC to the other QTH. Until then, is there something special I need to do to make both RRCs work on the same network?
Thanks,
/Rick