There are three main choices for dispensers. First, there are peristaltic pumps, which can precisely dispense nanoliter volumes of liquid with very little priming necessary; these are self-priming. Second are microprocessor-controlled syringes, which, like peristaltic pumps, can dispense nanoliter volumes but with much more rapid output and higher precision. In general, syringe-operated dispensers require more priming than peristaltic pumps, but the amount of priming depends on the system. Finally, there are hybrid detection systems that combine both technologies in one unit; in addition to liquid handling, such systems perform washing functions.