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Black 18-inch USB-A to DB9 serial adapter cable with moulded connectors

Tripp Lite

Tripp Lite U209-18N-NULL 18in USB converter

SKU CH-AFHG-JMMJQ MPN U209-18N-NULL

18-inch USB 2.0 to DB9 null-modem adapter with FTDI chipset, 256 Kbps speed and COM retention for Windows, Mac and Linux

  • Cable length18 in (45.7 cm)
  • Adapter typeUSB to VGA
  • First connector1x USB 2.0 male
  • Second connector1x VGA female
  • Product colorBlack
  • DetailsSystem Requirements: Computer or other device with available
  • Null-modem adapter resolves DCE/DTE conflicts without extra cables
  • FTDI FT232RL chipset enables COM retention after disconnect or reboot
  • 18 in cable length fits easily into a laptop bag
  • Powered from the USB 2.0 port with no external supply needed
  • 256 Kbps transfer rate doubles built-in serial port speed

USB to Null Modem Serial Adapter

The Tripp Lite U209-18N-NULL connects a USB 2.0 port to a DB9 serial device using an integrated FTDI FT232RL chipset. It requires no external power and supports Windows, Mac OS X 10.3 or later, and Linux. The 18-inch cable includes COM retention to preserve port assignments across reboots.

Sustained Data Transfer Behaviour

The adapter maintains speeds up to 256 Kbps during continuous operation, which is twice the rate of a standard built-in serial port. Premium foil and braid shielding reduces EMI/RFI line noise that can corrupt long transfers. The FTDI chipset handles flow control reliably without driver intervention under load.

DB9 Serial Interface Limits

The DB9 connector and null-modem wiring cap throughput at 256 Kbps regardless of the USB 2.0 host capability. Cable length is fixed at 18 inches, limiting placement flexibility for rack or industrial equipment. Buyers needing longer runs or higher baud rates must choose a different interface.

How it compares

Measured against everything we stock in USB Adapter Cables & Dongles, at today’s prices. Recalculated every night.

Price $27.99
Pricier than about 84% of the 1,430 comparable items (median $14.99).

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Specifications

Product
Brand nameTripp Lite
Model nameU209-18N-NULL
Product colorBlack
Adapter typeUSB to VGA
Ports & slots
First connector1x USB 2.0 male
Second connector1x VGA female
Size & build
Cable length18 in (45.7 cm)
Shipping weight0.08 kg
Package size122 × 94 × 38 mm
In the box
In the boxU209-18N-NULL USB to Null Modem Serial FTDI Adapter Cable (USB-A to DB9 M/F), 18 in
Driver CD
Owner’s manual

Questions about this item

Does the 18in cable draw any power or generate heat when left plugged in all day?

No external power source is required; the adapter draws only the small amount of current supplied by the USB 2.0 port and runs cool during continuous use.

What port must my computer already have to use this adapter?

An available USB 2.0 Type-A port is needed, plus a supported OS — Windows XP or later, Mac OS X 10.3 or later, or Linux.

Will the COM retention keep my legacy serial device on the same port after a reboot?

Yes, the integrated FTDI FT232RL chipset provides COM retention so the assigned COM value is automatically reassigned after disconnection or reboot.

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