
4 Port Native PCI Express RS232 Serial Adapter Card with 16550 UART
StarTech ID: PEX4S553
The PEX4S553 4-Port Native PCI Express RS232 Serial Adapter Card with 16550 UART lets you add 4 RS232 
(DB9) serial ports, using a single PCI Express expansion slot.
Based on a native single-chip design, this 4-port serial adapter card allows you to harness the full capability 
offered by PCI Express (PCIe), while reducing the load applied to the CPU by as much as 48% over 
conventional bridge-chip serial cards.
The RS232 Serial Adapter Card includes 4 half-height/low-profile brackets, allowing the card to be installed into 
almost any PC case, regardless of form factor.
Backed by a StarTech.com Lifetime warranty and free lifetime technical support.
Applications
POS retail applications in grocery stores, and any other retail store to control keyboards, cash drawers, 
receipt printers, card readers / card swipes, scales, and elevated displays on poles 
Bank teller workstations in either full profile or low profile versions to control their serial devices such as 
cash drawers, card readers / card swipes, printers, keypads / pinpads, pen pads 
Self-service automated machines and kiosks to control serial devices such as scales, touchscreens, 
magnetic card readers, bar code scanners, receipt printers, label printers 
Standard ATM automated teller machines to control keypads, receipt printer, card readers / card swipes, 
touchscreen LCD's, camera control, etc. 
Used to control multiple surveillance / security cameras in a parking structure, office building, etc.
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Features
Four high speed RS232 serial ports, with support for data transfer rates up to 128000bps 
256-byte deep FIFO per transmitter and receiver 
Native single-Chip, single lane PCI Express 
Includes half-height/low profile mounting brackets 
Built-in 16C450/550 compatible UART 
Compliant with PCI Express Base Specification 1.1
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Technical Specifications
Warranty Lifetime 
Bus Type PCI Express 
Card Type Standard Profile (LP bracket incl.) 
Chipset ID ASIX/MosChip - MCS9904CV-AA 
Interface Serial 
Port Style Integrated on Card 
Ports 4 
Data Bits 5, 6, 7, 8 
FIFO 256 bytes 
Max Baud Rate 128 Kbps 
Parity 5, 6, 7, 8 
Serial Protocol RS-232 
Connector Type(s) 1 - PCI Express x1 Male 
External Ports 4 - DB-9 (9 pin; D-Sub) Male 
Microsoft WHQL Certified Yes 
OS Compatibility Windows® 10 (32/64), 8 / 8.1 (32/64), 7 (32/64), Vista (32/64), XP (32/64)
Windows Server® 2012, 2008 R2, 2003 
Mac OS® 10.10 
Linux 
Color Green 
Product Height 0.7 in [19 mm] 
Product Length 4.7 in [120 mm] 
Product Weight 2.8 oz [80 g] 
Product Width 5.1 in [130 mm] 
Humidity 5~85% RH 
Operating Temperature 0°C to 50°C (32°F to 122°F) 
Storage Temperature -20°C to 60°C (4°F to 140°F) 
Shipping (Package) Weight 0.5 lb [0.2 kg] 
Included in Package 1 - 4 Port PCI-Express RS-232 Serial Card 
Included in Package 1 - Bracket with 2 DB9 male ports 
Included in Package 4 - Low Profile Brackets 
Included in Package 1 - Driver CD 
Included in Package 1 - Instruction Manual
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Certifications, Reports and Compatibility
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