Not totally certain but I think DTR to DSR, DCD is not used. In Windows you can use either CTS/RTS or DTR/DSR for hardware handshaking. Often the PC's CTS is connected to its own RTS at the remote end of the cable (to verify that a cable is plugged in) and DTR/DSR are usd to gate the data flow. /\/\/\/*=Martin ----- Original Message ----- From: "Bob Barr" To: Sent: Tuesday, November 20, 2001 11:50 AM Subject: [EE]: RS-232 connections I'm interfacing a device to the RS-232 port on a PC and would appreciate suggestions regarding the required connections. I've got a 9-pin female connector on the device and I'm using a straight-through female-to-male cable from the PC to the device. So far, I have ground, device Txd and device Rxd on pins 5, 2, and 3 respectively. I can communicate to and from the device with ProComm. So much for the easy part. :=) My real issue is looping back the handshake lines to most easily interface to a PC. I'd like to avoid forcing any changes to the PC's default handshake settings. For this application, I don't need any hardware handshaking so I'm planning to jumper the appropriate pins together at the device. I'm fairly certain that RTS and CTS (pins 7 and 8) need to be connected. Should I also make a connection between DCD, DTR and DSR (pins 1, 4, and 6)? (DCD to DTR looks most likely but I'm not at all sure about that.) Any suggestions? Thanks, Bob -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.