UGREEN DB9 RS232 Female-to-Female Cable, 1.5m (20149)
Overview
This cable does not contain a USB converter, serial controller or protocol electronics. Both connected devices must already use true RS232 electrical signalling, compatible pin assignment and matching communication settings.
- cable length
- mates with compatible male serial ports
- not a null-modem crossover cable
- no USB conversion or driver electronics
What it does well.
Key features
These are the functions that define this SKU. They are intentionally separated from performance assumptions so the connector, protocol and operating role stay clear.
- DB9 female connectors at both ends for compatible DB9 male equipment ports.
- Straight-through RS232 signal path retains the endpoint wiring rather than crossing transmit and receive internally.
- 1.5m cable length suits desk, rack, laboratory and industrial-instrument connections.
- Thumb screws on both connectors help resist accidental unplugging and vibration.
- Foil shielding and moulded connector shells are described for ordinary signal protection and handling.
- Passive construction needs no driver because it does not create a serial port or translate protocols.
Performance and planning
This guide separates the physical connector, protocol, speed ceiling and host requirements so that a familiar-looking plug is not mistaken for guaranteed compatibility. Performance examples are planning references, not promises: the source device, destination device, controller, operating system, cable chain, file system and workload can all become the limiting factor.
RS232 reliability depends on the endpoint transmitters/receivers, cable environment, baud rate, grounding, wiring and handshake use. The cable cannot compensate for incompatible endpoint settings.
A 1.5m run is modest for many RS232 applications, but electrically noisy industrial installations can still need careful routing and grounding. Keep the cable away from motors, relays and high-current power conductors where practical.
Do not judge serial compatibility by connector gender alone. A successful session requires the same baud rate, data bits, parity and stop bits, plus the correct flow-control arrangement.
Use scenarios
The following examples show realistic ways to use the product while retaining the compatibility and safety checks described elsewhere in this guide.
Industrial equipment. Connect a controller or instrument with a DB9 male port to another compatible RS232 endpoint using the required straight-through wiring.
Modem or serial peripheral. Link compatible serial devices that explicitly call for a straight-through DB9 cable rather than a null-modem crossover.
Laboratory bench. Use the screw locks for repeatable instrument or measurement connections where both endpoint manuals confirm RS232.
POS and service systems. Connect supported legacy equipment after confirming protocol, pinout, port gender and application settings.
Permanent routed link. Route the 1.5m lead with strain relief and separation from power cabling; leave access to loosen the screws for service.
Setup and usability guidance
Use this sequence as a practical installation checklist. If the connected equipment manual gives a stricter instruction, follow the equipment manufacturer’s procedure.
- Confirm that both endpoints are true RS232 and provide DB9 male sockets.
- Check that the equipment manuals specify a straight-through cable; if either calls for null modem, crossover or a proprietary pinout, stop.
- Power down equipment if its manufacturer instructs this for serial cabling and close any active serial session.
- Align the first DB9 female connector without bending pins or forcing the shell, then tighten both screws evenly by hand.
- Route the cable away from pinch points and strong electrical noise, leaving a relaxed bend behind each connector.
- Attach the second DB9 female end to the other compatible port and tighten its screws gently.
- Configure identical baud, framing and appropriate flow control on both endpoints, then test with a known low-risk command.
Compatible devices and systems
Compatibility is conditional on physical connector, electrical or storage protocol, host support, software and the complete system design. A matching plug alone is not enough.
- Two devices with DB9 male connectors and true RS232 electrical interfaces.
- Straight-through signal assignment expected by both endpoints; not null-modem by default.
- Equipment whose transmit/receive roles and handshake lines are compatible through a straight one-to-one path.
- Computers only when they already have the matching physical RS232 port or use a separate compatible serial adapter.
- Industrial controllers, instruments, modems, POS devices and selected peripherals only when their manuals specify this cable type.
- Operating system is irrelevant to the passive cable itself; serial-port hardware, application and endpoint protocol determine usability.
What this product does
Use this product for the narrow functions below. Keeping the role specific makes troubleshooting easier and avoids buying it for an unrelated conversion task.
- Connects two compatible DB9 male RS232 ports through female-ended plugs.
- Carries existing RS232 signals through a passive straight-through cable path.
- Provides 1.5m reach and screw retention at both ends.
- Preserves signal assignments rather than performing active protocol translation.
- Requires no driver of its own because no electronic interface is added.
What this product does not do
These exclusions are as important as the feature list. They distinguish this model from converters, powered accessories and visually similar products.
Important: If your required function appears in this exclusion list, choose a purpose-built product for that function rather than adding unverified adapters.
- It does not create a serial COM port from USB.
- It does not cross transmit and receive as a null-modem cable.
- It does not convert RS232 to TTL UART, RS422, RS485, Ethernet or parallel.
- It does not correct incompatible baud, parity, stop-bit or flow-control settings.
- It does not guarantee that all nine pins are used identically by proprietary equipment.
- It does not supply operating power to either connected device.
What to do
Good installation and handling habits protect data, equipment ports and connection reliability.
- Compare both endpoint manuals for connector gender, RS232 standard, pin assignment and cable type.
- Confirm straight-through rather than null-modem wiring before installation.
- Align connectors carefully and tighten both screws evenly by hand.
- Match serial communication parameters on both endpoints.
- Route away from high-current cables, motors and relay coils where possible.
- Label the cable and endpoint settings for future service work.
What not to do
Avoid these common mistakes even when the connectors appear to fit.
- Do not force a mismatched connector or straighten damaged pins while equipment is connected.
- Do not substitute this cable when the manual specifies null modem or a proprietary pinout.
- Do not connect it to VGA merely because VGA also commonly uses a D-sub shell.
- Do not expect USB, Ethernet or another protocol to pass through DB9 adapters without active conversion.
- Do not overtighten thumb screws, pull by the wire or leave the cable bearing equipment weight.
- Do not disconnect during firmware, configuration or transactional activity.
Warnings and limitations
Review every point before connecting valuable equipment or irreplaceable data. Stop use if the setup does not match the documented interface.
Stop and recheck: Disconnect if connectors are forced, hardware becomes abnormally hot, data becomes unstable or the electrical/protocol role is uncertain.
- DB9 is a connector shape, not a protocol guarantee. Confirm true RS232 electrical levels on both sides.
- Straight-through and null-modem cables are not interchangeable. Incorrect wiring usually prevents communication and can be unsafe for sensitive equipment.
- Some manufacturers use proprietary DB9 pin assignments. Follow the equipment pinout rather than assuming a universal application.
- The passive cable cannot isolate ground potential or suppress severe industrial electrical noise.
- Screw locks prevent casual removal but do not justify suspending equipment from the cable.
- Disconnect and investigate any abnormal heat, odour, visible damage or repeated communication errors.
Check before ordering
A minute spent checking the complete signal path is more useful than choosing by connector shape or headline speed alone.
- Both device ports are DB9 male.
- Both ports use true RS232 electrical signalling.
- The manuals specify a straight-through connection, not null modem/crossover.
- The pin assignment and DTE/DCE roles are compatible.
- 1.5m is the appropriate installed length and the cable can be routed with strain relief.
- Both endpoints can be configured for matching baud, framing and flow control.
Care and troubleshooting
Start with the simplest known-good path, change one variable at a time and protect important data before testing storage or configuration workflows.
- Cover or bag unused connectors, coil the cable loosely and protect the pins/sockets from dust, moisture and impact.
- For no communication, recheck straight-through requirement, connector gender, endpoint power, selected port and complete framing settings.
- For garbled characters, match baud, data bits, parity and stop bits exactly, then inspect grounding and electrical noise.
- For intermittent operation, tighten screws gently, inspect the cable near strain relief and reroute away from switching power equipment.
- If the application requires USB, add a separately selected active USB-to-RS232 adapter with compatible connector gender and driver support.
At a glance.
- Product
- Passive DB9 RS232 female-to-female cable
- SKU
- 20149
- Cable length
- 1.5m
- Connector 1
- DB9 female
- Connector 2
- DB9 female
- Mating equipment ports
- Compatible DB9 male
- Signal standard
- RS232 when both endpoints are compatible
- Wiring type
- Straight-through; not null modem
- Active conversion
- None
- Driver
- None for the passive cable
- Retention
- Thumb screws on both connectors
- Shielding
- Foil-shielded construction described in listing
- Power delivery
- None
- Protocol exclusions
- Not USB, Ethernet, TTL UART, RS422, RS485, VGA or parallel conversion
- Required settings
- Matching baud, data bits, parity, stop bits and applicable flow control
- In the box
- 1 × UGREEN 1.5m DB9 RS232 female-to-female passive cable, SKU 20149.
No USB-to-serial converter, null-modem adapter, gender changer, power supply or serial software is identified as included.
Any separate active adapter must match the cable connector gender, RS232 standard, driver and endpoint wiring.
The table consolidates the model facts and deliberately states conditional performance where the result depends on the wider system.
Package contents below reflect the current product record and gallery presentation. Accessories shown only as connected examples are not automatically included.
Questions buyers ask.
What connectors are on SKU 20149?
Both ends are DB9 female; they mate with compatible DB9 male equipment ports.
Is this a null-modem cable?
No. It is a straight-through passive cable. Use it only when both endpoint manuals call for that wiring.
Does it convert USB to RS232?
No. There is no USB connector or conversion controller. A separate active USB-to-RS232 adapter is required for a USB-only computer.
Will it work with every DB9 port?
No. Both ports must use true RS232, compatible pin assignments and the required straight-through topology.
Is DB9 the same as VGA?
No. Connector families may look related, but VGA is video and this cable is for compatible RS232 serial equipment.
Does the cable need a driver?
No. It is passive. Any serial adapter or application used with it can have separate driver and software requirements.
What length is it?
this SKU is 1.5 metres.
Why are there thumb screws?
They hold the D-sub connectors evenly against compatible equipment sockets. Tighten by hand without excessive force.
Why is there no communication?
Check true-RS232 support, straight-through versus null modem, pinout, DTE/DCE roles, equipment power and all serial settings.
Can it carry RS485 or RS422?
No. Use cabling and an active interface designed for the electrical standard.
Does it power the equipment?
No. Each device needs the power source specified by its manufacturer.
Can I disconnect during configuration?
Avoid disconnecting during firmware, configuration or transaction activity. Close the session and follow the equipment procedure first.