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roaming | well, kind of. as long as the null modem cable ONLY includes pins 2, 3, and 5, then yes. BUT, even then, a null modem cable switches pins 2 and 3, so you're not going to get the communication you expect.
For example, if the AL device is expecting to RECEIVE a signal on pin 2, then the 277885A1 cable by itself will provide that signal (see the pinout in the earlier post - pin 2 on the receiver goes to pin 2 at the 9-pin, and this is the Receiver Transmit signal). BUT, if you put a null modem into the mix, then the null modem takes the signal from 2 and puts it on 3, which, in this case, would most likely be the pin that Ag Leader is using to TRANSMIT back to the receiver. So you would actually need one null modem to get rid of the power problem (assuming the null modem does not have pins 4 and 6, as described above). Then you would need ANOTHER null modem to cancel out the pin-switching, and then you still need your 277885A1.
Now, IF Ag Leader's device is wired to communicate via null modem (where they are TRANSMITTING on pin 2 and RECEIVING on pin 3, then one null modem + 277885A1 would work fine. (again, assuming the null modem does not have pins 4 & 6.)
If the null modem DOES have pins 4 and 6, they will also typically be switched, so you're still sending power to the receiver, just through a different pin. Still not a good situation. I think Ted's solution is probably the best.
FMI: http://en.wikipedia.org/wiki/Null_modem | |
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Torn or Tedbear
