Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B UNSW 1.1.4 (IPS) 85/07/04; site ipso.OZ Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!think!harvard!seismo!munnari!basser!ipso!craigb From: craigb@ipso.OZ (Craig Bevins) Newsgroups: net.dcom Subject: Re: Definition of "null modem" cable Message-ID: <196@ipso.OZ> Date: Mon, 2-Sep-85 21:00:09 EDT Article-I.D.: ipso.196 Posted: Mon Sep 2 21:00:09 1985 Date-Received: Thu, 5-Sep-85 20:22:44 EDT References: <195@almsa-1> Organization: IPS Radio and Space Services. Sydney, Australia. Lines: 42 In article <195@almsa-1> control@almsa-1 (William Martin) writes: > What is the exact definition of a "null modem" cable? Does the term > *only* mean that the connections to pins 2 and 3 on a DB25 RS232 > connector on each end are interchanged, or does it also imply > connections of other pins or the shorting or cross-connecting of > certain pins (like 1, 7, 6, and 20)? The very term "null **modem** cable" suggests to me that it should carry modem control signals. I have the following diagram of "the standard DEC null modem cable" (whatever that implies) .... 22 -----------o----------\ /----------o----------- 22 | X | 20 -----------(----------/ \----------)----------- 20 | | 8 -----------(------- ------)----------- 8 | | | | 7 -----------(------(----------)-----)----------- 7 | | | | 6 ------------ | | ----------- 6 | | 5 ------------ -----------)-----o---------- 5 | | | 4 -----------o------------------ ----------- 4 3 ----------------------\ /--------------------- 3 X 2 ----------------------/ \--------------------- 2 1 ---------------------------------------------- 1 Craig Bevins. IPS Radio and Space Services. P.O. Box 702, Darlinghurst. N.S.W. 2010. Australia. Phone: +61 2 269 8621 Telex: AA20663 IPSO UUCP: seismo!munnari!ipso.oz!craigb ACSnet: craigb@ipso.oz ARPA: craigb%ipso.oz@seismo.css.gov CSNET: craigb@ipso.oz