🧠 DB9 to DB9 Straight‑Through Serial Cable (Female ↔ Female)
 
(RS‑232 Serial Cable • 9‑Pin D‑Sub Female to Female • Direct Pin Mapping)
 
This cable links two DB9‑equipped devices for serial communication using a 1:1 pinout. It is typically used with equipment that exposes male DB9 connectors and expects a straight‑through connection.
 
🔧 Cable Form
DB9 female connector on both ends
Straight‑through wiring: pin 1 → pin 1, pin 2 → pin 2, etc.
Shielded cable with molded strain relief
Lengths range from 6ft to 10ft
RS‑232 compliant
 
🖥️ Compatible Devices
Industrial controllers (PLCs, CNC machines, sensors) with male DB9 ports
Networking equipment (routers, switches, console servers) with male DB9 console ports
External modems with male DB9 connectors
Legacy computing gear (lab instruments, GPS receivers, barcode scanners)
✅ Any device pair with male DB9 ports expecting direct RS‑232 signaling
 
✅ Common Uses
🔄 Serial communication between host and peripheral devices
🔌 PC to modem or router to console setups (when both expose male DB9 ports)
🧩 PLC to sensor/controller links in industrial automation
🧪 Legacy device interfacing for lab or field 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 male DB9 ports on both devices
 
🛠️ Quick Tips for Beginners
🧭 Confirm both devices have male 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