Add four esd protected rs232 ports with 5v or 12v selectable power output through a pci express slot the pex4s553s 4 port pci express serial card lets you add four esd protected rs232 ports with 5v or 12v selectable power output through a pci express slot ideal for industrial environments this 4 port serial card offers built in 15kv esd protection which helps prevent damage to connected devices in the event of line surges and electro static discharge plus for devices that require ad