If the Instrument Control or Autosampler Control Options have been purchased, Clarity needs a digital means to communicate with the instruments. For many systems, this is RS232, chosen because it is not plug and play (and hence boots up the same way every time) and is not dependent upon firewall or network issues to maintain seamless communication with the HPLC system. The problem is that most modern computers have only one, or even no RS232 ports at all.
One way to obtain RS232 ports is to use a USB to RS232 converter. These are usually very cheap (£20) and only provide a single RS232 port which doesn't work very well, or are extremely expensive (£300 +). The MultiCOM is priced in between, has six COM ports and works very well. Henc many customers buy this to use for other applications.
It has the possibility to be powered externally, but will usually function well using the power from the PC, by just plugging into a USB port. Clarity requires its security dongle to be plugged into a USB port, but the MultiCOM has its own port for the dongle, so even if the computer has only one free USB port, this is not a problem.