The LiQuilaz Particle Counter communicates via RS-485 protocol, so communication accessories are required.Depending on the configuration, you may need two cables and a BB485 converter. If the LiQuilaz instruments are daisy-chained (i.e. connected in series), a standard nine-pin serial cable can connect the two instruments.If the computer does not have a nine-pin serial port, a USB-to-serial converter is also required.