[RTTY] IC-7100

[Mark]

Has anyone interfaced an IC-7100 to N1MM+? I'm having trouble and I 
think the problem is with the radio. Am I correct in saying that I need 
a cable that connects between the ICOM's DATA jack (a 2.5mm stereo plug) 
to my computer's serial port? I built a OPC-152R cable from drawings I 
found on the web. The radio schematic shows an internal RS232 to logic 
converter chip connected to the DATA jack. But a check with a scope 
shows no voltage present on either pin on the plug when inserted into 
the jack. I should see a negative voltage on the TX part of the jack but 
there is nothing. Before I contact ICOM support I would like to know if 
I'm doing this right.
Thanks,
K5XH