Xref: utzoo comp.periphs:646 comp.terminals:507 Path: utzoo!mnetor!uunet!husc6!bbn!gatech!mcnc!ecsvax!ehr From: ehr@ecsvax.UUCP (Ernest H. Robl) Newsgroups: comp.periphs,comp.terminals Subject: Re: Help -- Making a modem with DB9 connector --> DB25 Message-ID: <4299@ecsvax.UUCP> Date: 11 Dec 87 20:01:35 GMT References: <860@seradg.Dayton.NCR.COM> <3150@batcomputer.tn.cornell.edu> Organization: UNC Educational Computing Service Lines: 52 Keywords: US Robotics modem DB9 DB25 Summary: DB9 serial connections On AT-type machines the pins on a DB9 serial connector are: 1 CD 2 RD 3 TD 4 DTR 5 Sig.Grnd. 6 DSR 7 RTS 8 CTS 9 RI For straight-through cables DB9 on computer to DB25 on modem, we have used the following: DB25 side DB9 side pin 2 to pin 3 pin 3 to pin 2 pin 4 to pin 7 pin 5 to pin 8 pin 7 to pin 5 pin 8 to pin 1 pin 20 to pin 4 pin 22 to pin 9 For a null-modem (DB9 computer to DB25 computer) we have used the following: DB25 side DB9 side pin 2 to pin 2 pin 3 to pin 3 pins 4&5 to pin 1 pin 6 to pin 4 pin 7 to pin 5 pin 8 to pins 7&8 pin 20 to pin 6 pin 22 to pin 9 Since you are going from a DB9 modem to a DB25 machine, the above may or may not work. Some electronics stores, including Radio Shack computer centers now sell DB9 to DB25 adapters. I presume they are wired as in the first example above. Hope this helps. -- Ernest -- My opinions are my own and not necessarily IBM-compatible.--ehr Ernest H. Robl (ehr@ecsvax) (919) 684-6269 (w) Systems Specialist, Library Systems, (919) 286-3845 (h) Perkins Library, Duke University, Durham, NC 27706 U.S.A.