Watch out for P20 and K1!

Just a heads up for those putting the boards together... I hope this will save someone else's sanity :-)  Make sure there are jumpers on both P20, and K1 (pin 1 and pin 2.)  P20 enables the 12v side to enable receive and transmit.  K1 controls transmit, so if pin 1 and pin 2 are open (not jumpered), it will instantly get stuck in transmit.  After a couple of hours of frustration, I remembered this the hard way...