25 PIN D-SUB FEMALE to Computer
25 PIN D-SUB FEMALE to Printer
A DB-25 to DB-25 serial printer cable connects a computer’s RS-232 serial port to a serial printer using two 25-pin D-subminiature connectors. The cable crosses Transmit Data and Receive Data between the two devices and pairs the flow-control lines accordingly. It operates under TIA/EIA-232-F (formerly EIA RS-232-C), the standard governing data interchange between Data Terminal Equipment and Data Circuit-Terminating Equipment using serial binary signals. Serial printer ports of this type were common on PCs and compatible systems from the early 1980s through the 1990s.
| D-Sub 1 | D-Sub 2 |
|---|---|
| Receive Data | 2 |
| Transmit Data | 3 |
| Clear To Send + Data Set Ready | 5 + 6 |
| Carrier Detect + Data Terminal Ready | 8 + 20 |
| Ground | 7 |
Signals
- TxD — Transmit Data; carries serial data from the computer to the printer (DB-25 pin 2 on the computer side connects to pin 3 on the printer side).
- RxD — Receive Data; carries serial data from the printer to the computer (DB-25 pin 3 on the computer side connects to pin 2 on the printer side).
- CTS — Clear To Send; flow-control input indicating the remote device is ready to receive data.
- DSR — Data Set Ready; indicates the remote device is powered and ready.
- DCD — Carrier Detect; asserted by the remote device to signal an active connection.
- DTR — Data Terminal Ready; asserted by the local device to signal readiness.
- GND — Signal Ground; common reference for all RS-232 voltage levels (DB-25 pin 7).
Notes
The D-Sub 1 column lists signal names for the computer side without explicit pin numbers; under TIA/EIA-232-F the DB-25 DTE assignments are: pin 2 = TxD, pin 3 = RxD, pin 5 = CTS, pin 6 = DSR, pin 7 = Signal GND, pin 8 = DCD, pin 20 = DTR. The D-Sub 2 column gives the corresponding printer-side pin numbers, confirming the TxD/RxD cross (computer pin 2 to printer pin 3, and computer pin 3 to printer pin 2). The handshake lines CTS and DSR on the printer side (pins 5 and 6) are tied together, as are DCD and DTR (pins 8 and 20), to satisfy flow-control requirements without requiring full modem-style handshaking. RS-232 logic levels are: Mark (logic 1) = −3 V to −15 V; Space (logic 0) = +3 V to +15 V; maximum cable capacitance is 2500 pF per TIA/EIA-232-F.