Solution:

ZXTxx-RM One way Comm If the Radio modems are connected for one way communication, with TX and GND on one side and an RX and GND on the other side, this will not work. Below is a description from Engineering on why this does not work: This is due to the fact that the 232 transceiver is set up in auto online mode, an oversight on our part. This means it needs to see RS232 signals to activate. The modem with TX and GND should work ok but the one with RX and GND will not work without the TX line, or the RTS line connected to a 232 signal. If using a 12v supply, could just jumper the +12 to the RTS line and it should work just fine. ZXT9-RM ZXT24-RM Peter Fitzpatrick 5/26/11