When choosing a DB9 to DB9 null modem cable, the goal is reliable cross-wiring between two DTE devices for seamless data transfer. This guide highlights five well-matched options and clarifies which buyer each is best for. If you need cross-wired RS232 connections for industrial equipment, point-to-point networking, or legacy hardware, these cables cover common lengths and handshaking configurations.
Buyers can skim the quick-reference table below to compare key specs at a glance.
| Product | Length | Wiring | Best For |
|---|---|---|---|
| StarTech.com 10′ RS232 Serial Null Modem Cable | 10 ft | DB-9 (F) to DB-9 (F), null modem | Longer runs between devices |
| DTECH 6ft DB9 to DB9 RS232 Cable | 6 ft | DE9, cross TX/RX, no handshake | Budget, simple data transfer |
| StarTech 2m DB9 RS232 Null Modem Cable | 6.56 ft | DB-9 (F) to DB-9 (F), cross wired | Compact deskside setups |
| StarTech 10 ft DB9 RS232 Null Modem Cable F/M | 10 ft | DB-9 (M) to DB-9 (F), null modem | Mixed device types |
| DTECH 15 Feet DB9 Serial Null Modem Cable | 15 ft | Full handshaking, cross TX/RX | Long-distance or devices needing handshaking |
StarTech.com 10′ RS232 Serial Null Modem Cable
Product: StarTech.com 10′ RS232 Serial Null Modem Cable — Null modem cable with DB-9 female to DB-9 female connectors, 10 ft length. This cable is best for users who need a straightforward, medium-length crosswired connection between two serial devices.
Best for: Long-distance desk setups or equipment that sits apart on a lab bench. The DB-9 female connections reduce mating stress on legacy equipment.
Why selected: It provides a simple, reliable cross-wire solution without extra handshake circuitry, making it a solid default for legacy RS232 tasks.
Caution: Ensure both devices support RS-232 signaling and that you don’t require hardware handshaking for your specific application.
DTECH 6ft DB9 to DB9 RS232 Cable
Product: DTECH 6ft DB9 to DB9 RS232 Serial Cable, Male to Male, simple null modem cord with 3-wire cross. It’s best for basic data transfer between two DTE devices when you don’t need handshaking lines.
Best for: Budget-conscious users who need a short, ready-to-connect null modem cable for quick setups or temporary data exchanges.
Why selected: The 3-wire crossed design handles TX and RX crossovers cleanly, with a shielded cable for stable data transmission in typical office or lab environments.
Caution: This model does not support hardware handshaking. If your devices require RTS/CTS or DTR/DSR lines, consider a full-handshaking option.
StarTech 2m DB9 RS232 Null Modem Cable
Product: StarTech 2m DB9 RS232 Null Modem Cable, DB9 female to DB9 female, cross-wired, 2 meters long. It’s a compact option for tight spaces with two serial devices on a small desk.
Best for: Users who need a shorter, crosswired connection between two devices at a workbench or in a compact rack setup.
Why selected: The 2m length combines accessibility with a manageable cable footprint, reducing cable clutter while preserving cross-over data lines.
Caution: Verify connector gender requirements for your devices; this model is female-to-female, which may not fit devices expecting opposite gender compatibility.
StarTech 10 ft DB9 RS232 Null Modem Cable F/M
Product: StarTech 10 ft DB9 RS232 Null Modem Cable, DB-9 male to DB-9 female, cross-wired. This arrangement supports connecting mixed-gender devices over a longer distance.
Best for: Scenarios where one device is male-equipped and the other is female, and a longer reach is needed for data transfer.
Why selected: The longer length helps reduce strain on devices placed apart while maintaining reliable TX/RX cross-connection.
Caution: If both devices require identical gender connectors, verify if an all-female or all-male variant would be more suitable to avoid gender-related compatibility issues.
DTECH DB9 Serial Cable Null Modem 15 Feet
Product: DTECH 15 Feet DB9 RS232 Serial Cable Null Modem, male to female with full handshaking, cross-linked TX/RX, and longer reach. This option is designed for environments where a longer distance and handshaking are necessary.
Best for: Users needing extended cable length with full handshaking to support more complex RS-232 devices and flow control signals.
Why selected: The 7-wire design with handshaking supports more robust communication in networks with higher data integrity requirements.
Caution: Longer cables can introduce potential signal degradation if run over extended distances or near EMI sources; ensure proper shielding and routing.
Buying Guide
What should I consider when choosing a DB9 to DB9 null modem cable?
Key factors include length, connector gender, presence of handshaking signals, and whether you need shielded cable protection. Longer cables may incur minor signal loss; shielded cables help in electrically noisy environments.
What’s the difference between male-to-male, female-to-female, and mixed gender?
Male-to-male cables connect two female devices, while female-to-female connects two male devices. Mixed-gender cables connect devices with opposite connector genders. Choose the option that matches your devices’ ports to avoid adapters or adapters that could degrade performance.
When is handshaking necessary?
Handshaking lines (RTS/CTS, DTR/DSR) are needed when devices rely on flow control. If your devices communicate without hardware handshaking, a simple 3-, 4-, or 7-wire cross may suffice.
What about shielding and durability?
Shielded cables protect against EMI and improve reliability in industrial or office environments. Look for aluminum foil shielding and robust connectors with locking screws to ensure stable connections over time.
How do I verify compatibility?
Ensure both devices support RS-232 signaling and that the cable’s wiring aligns with the devices’ port configurations. If you encounter compatibility issues, verify the device’s documentation for required signals and any needed adapters.
What is a quick checklist for setup?
- Identify device ports and gender requirements.
- Choose appropriate length for your workspace.
- Decide if handshaking lines are required.
- Confirm wiring is null modem (crossed TX/RX).
- Secure cables away from heat, moisture, and EMI sources.
FAQ
- What is a null modem cable?
A null modem cable cross-connects TX and RX lines between two devices to enable direct serial communication without a modem.
- Do I need handshaking on a null modem cable?
Not always. If both devices support simple data transfer without flow control, you can use non-handshaking versions. For devices requiring RTS/CTS or DTR/DSR, choose a full handshaking variant.
- Can I use any length for RS232 connections?
Yes, within practical limits. Longer cables can introduce signal loss, so use shielded, quality cables for distances beyond a few meters.
- What if my devices have different connector genders?
Choose a cable with the appropriate gender on each end to match your devices directly, avoiding adapters that may affect signal integrity.
- Is DB9 the same as DE-9?
Typically, yes; many vendors refer to it as DB9 or DE-9 interchangeably. Confirm the connector type is DB-9 female or male as needed.
Summary
The five highlighted cables offer a mix of lengths, genders, and handshaking options to cover common RS232 null modem needs. For longer desk-to-device links, consider the 10 ft and 15 ft variants. For compact setups, the 2 m and 6 ft options balance space with reliability. When devices require full handshaking, the 15 ft DTECH cable provides a capable solution. Always confirm device compatibility and handshaking requirements before purchasing.