RJ45 to serial DE-9

On Feb 6, 4:08, r. 'bear' stricklin wrote: The way I usually do it is to cross wire like this: DTR -------------------- DSR \ DSR -- ------ DCD \ DCD -------------------- DTR Another way is to simply link all three together on each connector (with no DTR/DSR/DCD connections between the connectors). I usually also cross over RTS and CTS, or tie them together at each end. The logic is roughly like this: terminal connected to modem; terminal raises DTR to indicate that it's active (Data Terminal Ready) and it wants some attention. If modem is powered up, it replies by raising DSR (Data Set Ready) to indicate some kind of life. If it grabs a line, makes a connection, and gets a carrier tone in response, it raises DCD (Data Carrier Detect) to say so. I say "roughly" because it's actually different for full-duplex and half-duplex, and neither is quite what I've described above. However, that conveys the general sense. So in a situation where you have two terminals (or any other equivalent device, like a PC, printer, in fact any DTE or Data Terminal Equipment rather than DCE -- Data Communications Equipment) you create a "null modem" in between. When one side raises DTR, the other sees DSR, and vice-versa. When ever one sees DSR, it knows there's something there and it also sees DCD and thinks it's OK to transmit and receive (well, strictly speaking, only to receive). -- Pete Peter Turnbull Network Manager University of York