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One connector is assembled from each side of the hyphens. The frame ground on the 25 pin plug is optional and should only be connected on one side of the cable.
If you need Data Carrier Detect (DCD) on your cable (BBS programs, Unix Getty and so on) then:
The connections for DCD should be made on the same end of the cable.
| 25 Pin | 9 Pin | 9 Pin | 25 Pin | |||
| FG (Frame Ground) | 1 | - | X | - | 1 | FG |
| TD (Transmit Data) | 2 | 3 | - | 2 | 3 | RD |
| RD (Receive Data) | 3 | 2 | - | 3 | 2 | TD |
| RTS (Request To Send) | 4 | 7 | - | 8 | 5 | CTS |
| CTS (Clear To Send) | 5 | 8 | - | 7 | 4 | RTS |
| SG (Signal Ground) | 7 | 5 | - | 5 | 7 | SG |
| DSR (Data Set Ready) | 6 | 6 | - | 4 | 20 | DTR |
| DTR (Data Terminal Ready) | 20 | 4 | - | 6 | 6 | DSR |
| Connector | FEMALE (Holes) | MALE (Pins) |
| 25 pin DB25 |  |
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| 9 pin DB9 |  |
If you need information on the RS-232 standard please see:
RS-232 Standard Configuration & Pinout
Some of this valuable information was found at:
http://fly.hiwaay.net/~jfrohwei/tech/null-mod.html
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