I swiped this source from http://unix1.hials.no/~aoy/home_uk.html, it was so damn useful I was afraid it might disappear. Finding this document was one of the things that made me consider that the web might actually be useful. It saved me the trouble of walking across the street to my office to pull out a paper copy from the back of some hideous manual. The ambivalence I have towards this event exactly sums up my feelings for the net in general.
25pin 9pin 9p 25p FG 1 – X – 1 FG
TD 2 3 – 2 3 RD
RD 3 2 – 3 2 TD
RTS 4 7 – 8 5 CTS
CTS 5 8 – 7 4 RTS
SG 7 5 – 5 7 SG
DSR 6 6 – 4 20 DTR
DTR 20 4 – 6 6 DSR
Request To Send
Clear To Send
Data Set Ready
Data Terminal Ready
You assemble one connector from each side of the hyphens. The frame ground on the 25 pin plug is optional and should I have been told only be connected on one side of the cable. If you need Data Carrier Detect on your cable (BBS programs, Unix Getty and so on) then you should apply this patch. On a 25 pin plug you can connect pin 6 and 8 On a 9 pin plug you can connect pin 1 and 6 These connections should be made on the same side of the cable.
The standard for RS232 sets these signals on the various pins.
Common name RS232C Name Description 25pin 9 pin DCE Direction 1 AA x Protective Ground 2 TXD 3 BA I Transmitted Data 3 RXD 2 BB O Received Data 4 RTS 7 CA I Request to Send 5 CTS 8 CB O Clear to Send 6 DSR 6 CC O Data Set Ready 7 GND 5 AB x Signal Ground 8 CD 1 CF O Received Line Signal Detector 9 -- x Reserved for Data set Testing 10 -- x Ditto 11 x Unassigned 12 SCF O Secondary Received Line Signal Detector 13 SCB O Secondary Clear to send 14 SBA I Secondary Transmitted Data 15 DB O Transmission Signal Element Timing (DTE Source) 16 SBB O Secondary Received Data 17 DD O Receiver Signal Element Timing (DCE Source) 18 x Unassigned 19 SCA I Secondary Request to Send 20 DTR 4 CD I Data Terminal Ready 21 CG O Signal Quality Detector 22 9 CE O Ring Indicator 23 CH/CI I/O Data Signal Rate Selector (DTE/DCE Source) 24 DA I Transmit Signal Element Timing (DTE Source) 25 x Unassigned
I will not accept any responsibility for the correctness of this information nor any liability for damages that have been inflicted on you through the use of this information