On 2013-04-09 19:22, Dean Gibson AE7Q wrote:

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For some Icom radios (eg, the ID-880H and IC-2820H) that use the Icom OPC-1529R cable, it's a simple three-wire cable providing ground, TX, and RX. Presumably these are at RS-232C acceptable levels (that's a whole different discussion). Other cables (eg, the Yaesu one for the Yaesu FT-897D) have a little circuit board in the RS-232C/DB-9 shell that does level conversion (and needs power, except for the few radios where the cable provides the power). Still other cables, like the ones that split out TX and RX signals from a single wire, have additional circuitry for that purpose.

To see the complexity of this issue, see http://www.starrsoft.com/software/win96/cables/gre_cables.htm This cable and its internal circuitry (and power) are necessary in order to separate out TX from RX in a single-wire (plus ground) radio jack (like the IC-7000 has). The cable under discussion works perfectly to communicate with the Icom IC-7000 on my computer, and when Radio Shack was having a close-out sale, I bought four of them (@ $2.00 each). This cable requires DTR high and RTS low in order to work. Then I found the above article, which explains the numerous complaints I have seen on the Internet about this cable (and why the price was so low). Apparently there are issues with the cable, and the lower-powered serial ports that are commonly found on laptops ...

So, I don't use them any more; I use the RT Systems CT-29A cable with the IC-7000. The CT-29A works just fine with both DTR and RTS high on one serial port I have, but works on all of my serial ports with DTR low and RTS high.