🧠 DB9 to DB9 Straight‑Through Serial Cable (Male ↔ Female)
 
(RS‑232 Serial Cable • 9‑Pin D‑Sub Male to Female • Direct Pin Mapping)
 
This cable links two DB9‑equipped devices for serial communication using a 1:1 pinout. It’s commonly used in industrial, networking, and legacy computing environments.
 
🔧 Cable Form
DB9 male connector on one end
DB9 female connector on the other
Straight‑through wiring: pin 1 → pin 1, pin 2 → pin 2, etc.
Shielded cable with molded strain relief
Lengths range from 3ft to 100ft
RS‑232 compliant
 
🖥️ Compatible Devices
PCs and laptops with DB9 serial ports
Modems (external RS‑232 models)
Routers and switches with DB9 console ports
Industrial controllers (PLCs, sensors, CNC machines)
Embedded systems with DB9 serial interfaces
✅ Any device pair with opposite gender DB9 ports expecting direct RS‑232 signaling
 
✅ Common Uses
🔄 Serial communication between host and peripheral
🔌 PC to modem or router to console setups
🧩 PLC to sensor/controller links in industrial automation
🧪 Legacy device interfacing (GPS, barcode scanners, lab equipment)
🧵 Debugging and firmware flashing via serial console
 
🧠 Signal Format
⚡ RS‑232 standard
🔌 Straight‑through pinout:
Pin 2 (TX) → Pin 2 (TX)
Pin 3 (RX) → Pin 3 (RX)
Pin 5 (GND) → Pin 5 (GND)
Remaining pins map identically
🔁 No crossover — not suitable for direct PC‑to‑PC links
 
⚠️ Things to Watch Out For
📉 Not interchangeable with null modem cables (which cross TX/RX)
🔌 Both devices must expect straight‑through signaling
🧯 Using this cable in a null modem scenario will result in communication failure
📏 Gender matters — only works with DB9 male ↔ DB9 female port pairing
 
🛠️ Quick Tips for Beginners
🧭 Confirm both devices have opposite gender DB9 ports and expect straight‑through wiring
🔌 Use for host‑to‑peripheral setups, not peer‑to‑peer
🧪 For PC‑to‑PC or device‑to‑device links, use a null modem cable instead
🧯 Label clearly — DB9 cables look identical externally but differ internally