DB9 to DB25 Serial Cable
- DB9-to-DB25 passive serial transition cables and compact inline adapter
- Male/female combinations shown in the verified product cards below
- Signal-to-signal RS-232 mapping based on an approved pin table
- Molded PVC or serviceable metal-shell construction by model
- Custom length, shielding, labeling, packaging, and retention options
- Three-wire or hardware-handshake builds when documented by the buyer
- Continuity and short-circuit inspection against the released drawing
Custom DB9-to-DB25 Serial Cable for Legacy RS-232 Equipment
A DB9-to-DB25 serial cable connects equipment with different D-sub connector sizes while preserving the signal functions each device required. It is a passive assembly: it can route an RS-232 interface between 9-position and 25-position connectors, but it does not convert USB, Ethernet, voltage levels, or communication protocols.
“Straight-through” in this product family means that corresponding signal names are connected correctly between the DB9 and DB25 formats. It does not mean DB9 pin 1 goes to DB25 pin 1. BespokeCable confirms the connector gender, DTE/DCE relationship, data lines, handshake circuits, ground, shield, and retention hardware before production.
For other endpoint combinations, our D-Sub cable collection separates connector families and transition formats.
DB9 to DB25 Serial Cable Specifications
| Parameter | Available Choices | Confirmation Needed |
| Connector A | 9-position D-sub, male or female | Mating port gender and hardware |
| Connector B | 25-position D-sub, male or female | Mating port gender and hardware |
| Function | Passive RS-232 connector-format transition | DTE/DCE role and required signals |
| Wiring | Reduced-signal, full-handshake, or customer-defined | Approved signal-name-to-pin table |
| Hood | PVC molded or metal shell, depending on card | Clearance and serviceability |
| Shield | Project-defined foil, braid, or combined construction | Shell/drain termination method |
| Length | Standard or custom | Measuring points and tolerance |
| Identification | End labels, customer P/N, or serialized label | Exact text and placement |
| Verification | Continuity and shorts to approved drawing | Additional report requirements |
The approved quotation and drawing define final materials, dimensions, electrical limits, and compliance requirements.
Click here to learn more about the DB9-to-DB25 cable.
Group 1 — DB9 Female to DB25 Male Serial Cables
P/N: BC-CBD007-FMM
Metal-shell DB9-female to DB25-male serial transition for installations that need a serviceable hood and a defined shield termination. Confirm the DTE/DCE map before ordering.
P/N: BC-CBD007-FMP
Molded DB9-female to DB25-male cable for a documented RS-232 transition. Gender and pin mapping must match the two equipment ports.
P/N: BC-CBD007-MFP
Molded DB9-male to DB25-female assembly for equipment using the opposite mating genders. Supply the signal map; connector gender alone does not identify DTE or DCE.
P/N: BC-CBD007-FMA
Compact female-to-male adapter for installations that don’t need extra cable length. Its internal signal map still requires confirmation.
Change the Connector Size Without Changing the Interface
A passive DB9-to-DB25 serial cable connects suitable RS-232 endpoints with different D-sub contact counts. It does not create a serial port or convert RS-232 to TTL, RS-422, or RS-485. Confirm that both devices already provide the electrical interface the connection requires.
For two like-role DTE endpoints, a DB9 to DB25 null modem cable may be the appropriate wiring family instead. Select between the two from the equipment documentation, not the apparent gender of the plugs.
Map Signal Functions Across the Two Contact Counts
DB9 and DB25 RS-232 interfaces don’t map every corresponding signal to the same contact number. A signal-preserving transition therefore needs a cross-reference of functions, not a rule that joins identical numbers. Transmit, receive, ground, and any control lines must reach their intended destinations.
Include the DTE or DCE role of each endpoint and its flow-control requirements. “Serial cable” alone cannot resolve those details. We can work from a released connection table or review a documented existing assembly, with uncertainty resolved before approving the production map.
Select a Hood or Inline Adapter for the Available Space
A cable keeps the DB9 and DB25 ports apart and offers more routing flexibility. An inline adapter is compact but adds a rigid extension directly behind the equipment. Check its projection and the load from any attached equipment.
The cable versions offer different housing formats. Compare their dimensions, fastening access, and strain-relief arrangements in the installed position. A metal hood is not evidence of an environmental rating, and a molded hood is not automatically unsuitable for industrial equipment; the documented construction and route determine suitability.
Define the Route and Noise Environment
A short instrument lead and a cabinet-to-machine connection place different demands on the cable. State the length, serial settings, and route, including proximity to power wiring or moving parts. Cable construction and grounding need to be reviewed in that context.
If shielding is required, specify its termination at the shells or drain connection. Do not assume the correct scheme from the connector gender. For long or electrically difficult routes, review the complete communication design instead of relying on a passive cable to overcome every system limitation.
Send both equipment models, DB9 and DB25 gender, DTE/DCE role, required signals, baud rate, flow-control setting, cable length/tolerance, quantity, hood, shield termination, label text, and any report requirement.
Often, yes, when a verified drawing, continuity table, or known-good sample is available. The equipment revision and viewing direction should accompany the sample.
Yes. Provide the exact label text, barcode or serialization rule, placement, revision format, and packaging instructions.
State whether the length is connector-face to connector-face, housing to housing, or cable-only, and include the required tolerance.
Yes, when specified before quotation. Define whether you need a pass record, measured resistance limits, serial-number traceability, or a signed inspection report.
Related Products
Diagnosing a DB9-to-DB25 Replacement Before Ordering in Volume
Keep the original configuration visible
Start with photographs of both ports and a list of every cable or adapter between them. Record whether the previous connection worked and what changed before the fault appeared. This helps distinguish a replacement request from a new interface design.
Where a working reference exists, compare its wiring with the equipment manuals. A previous installer may have placed a crossover in an additional adapter. Omitting that part from the replacement request can produce a correctly manufactured cable that serves the wrong connection.
Change one part of the link at a time
During the pilot, keep known settings and endpoint hardware unchanged while evaluating the new assembly. Confirm the application can both send and receive, and exercise the required control-line behavior. A single successful message does not necessarily verify hardware handshaking.
If an upstream USB adapter is involved, record its hardware and driver version separately. The passive DB9-to-DB25 cable has no driver of its own; investigate host recognition problems at the active interface.
Turn the result into an ordering definition
After acceptance, record which equipment pair was tested, which wiring revision passed, and which installation dimensions are mandatory. A clear test scope is more useful than a blanket claim of compatibility with a machine brand.
Use that accepted definition for the production order. If the same plant has several similar controllers, identify their differences before sharing a cable part number across them. A connector photograph alone is not enough to approve that consolidation.
