Multi-parameter, computer controlled operation of a FACS II cell sorter

The ease of operation and versatility of a FACS II cell sorter were improved by replacing the original pulse height analyzer (PHA) with a computer-based dual parameter PHA and a single channel analyzer (SCA). An ND620 LSI-11 based PHA is now used to generate the sorting decisions. Sorting windows are created by intensifying one or more regions of any shape on the PHA single or dual parameter histograms. For three parameter operation, the third parameter SCA contols the dual parameter information sent to the analyzer. The SCA can also trigger an abort circuit during the PHA 15 microsecond analyzing dead time, improving the purity of the sorted fraction. The electronics that interfaces the new PHA to the sorter replaces all of the original FACS II analog signal processing circuitry with an interchangeable circuit board. The principles involved should apply to any cell sorter.