laptop serial port

The laptops we use have no serial ports or parallel ports, and I tried a different model from Targus (the PA075), and I never got it to work with the serial connections (Ademco, GE Alliance, Pass Point, IEI, & Napco specifically). Tech Support said it wasn't made for direct constant connections like that, only external modems and mice. Had great results with the Belkin F5U103, with all those serial connections, and an external modem for dialup downloaders. A co-worker got one of the $18 dollar models, and got very miced results. I've heard people recommend the serial port PCMCIA cards, but haven't tried them personally. I would not get the Targus, and call the manufacturers you are using to see if they have a preference (some recommend one specific model that they sell, but that's not a practical solution, one USB adapter for each maker).