Null Modem Wiring Schemas ------------------------- From gjohnson(@)dream.season.com Mon Oct 28 09:59:58 1996 Newsgroups: comp.terminals Subject: Pick a number of wires, almost any number . . . Date: 23 Oct 1996 22:13:28 GMT During my search for the best thing to do with six wires I helped someone that only had three and got the following response, which might be interesting to readers here. -- Gary Johnson "Rosebud . . ." gjohnson(@)season.com From: Francesco Potorti` F.Potorti(@)cnuce.cnr.it Newsgroups: comp.os.linux.networking Subject: Re: TCP/IP over null modem? gjohnson(@)dream.season.com (Reality is a point of view) writes: I wish I knew which connections were best when there are six wires available. I have this note. I copied it from various sources. The only one I really tried is the last one, to be used while connectin two PCs with the DOS program whose name I can't remember (standard with msdos > 5.0) 7 wires null modem connections for V24 protocol on RS-232 DTE DTE 2 [>]------\ /------[<] 2 TX [ ] \ [ ] 3 [<]------/ \------[>] 3 RX [ ] [ ] 4 [>]-\ /-[<] 4 RTS [ ] | | [ ] 5 [<]-+---\ /---+-[>] 5 CTS [ ] \ / [ ] 6 [<]----\ / /----[>] 6 DSR [ ] \/ \/ [ ] 7 [-]-----/\-/\-----[-] 7 GND [ ] / \ \ [ ] 8 [<]---/ / \ \---[>] 8 DCD [ ] / \ [ ] 20 [>]----/ \----[<] 20 DTR 3 wires null modem connections for V24 protocol on RS-232 DTE DTE 2 [>]------\ /------[<] 2 TX [ ] \ [ ] 3 [<]------/ \------[>] 3 RX [ ] [ ] 4 [>]-\ /-[<] 4 RTS [ ] | | [ ] 5 [<]-/ \-[>] 5 CTS [ ] [ ] 6 [<]-\ /-[>] 6 DSR [ ] | | [ ] 7 [-]-|-----------|-[-] 7 GND [ ] | | [ ] 8 [<]-+ +-[>] 8 DCD [ ] | | [ ] 20 [>]-/ \-[<] 20 DTR Null modem on the MISCO catalogue (DTE) DTE DTE 1 [-]---------------[-] 1 GND [ ] [ ] 2 [>]------\ /------[<] 2 TX [ ] \ [ ] 3 [<]------/ \------[>] 3 RX [ ] [ ] 5 [<]-\ /-[>] 5 CTS [ ] | | [ ] 6 [<]-\ /-[>] 6 DSR [ ] | | [ ] 7 [-]-|-----------|-[-] 7 GND [ ] | | [ ] 8 [<]-+----\ /----+-[>] 8 DCD [ ] \ [ ] 20 [>]------/ \----\-[<] 20 DTR Null modem on the MISCO catalogue (DCE) DCE DCE 1 [-]---------------[-] 1 GND [ ] [ ] 2 [>]------\ /------[<] 2 TX [ ] \ [ ] 3 [<]------/ \------[>] 3 RX [ ] [ ] 4 [>]-----\ /-----[<] 4 RTS [ ] \ / [ ] 5 [<]----\ \ /----[>] 5 CTS [ ] \/ \/ [ ] 6 [<]-----/\ /\-----[>] 6 DSR [ ] \ [ ] 7 [-]------/-\------[-] 7 GND [ ] / \ [ ] 20 [>]----/ \----[<] 20 DTR Null modem for PC DCE DCE 2 [>]------\ /------[<] 2 TX [ ] \ [ ] 3 [<]------/ \------[>] 3 RX [ ] [ ] 4 [>]------\ /------[<] 4 RTS [ ] \ [ ] 5 [<]------/ \------[>] 5 CTS [ ] [ ] 6 [<]-----\ /-----[>] 6 DSR [ ] \ / [ ] 7 [-]-------\-------[-] 7 GND [ ] / \ [ ] 20 [>]-----/ \-----[<] 20 DTR --