Keithley dual multiplexer plug in card 37xx series keithley 3730 the keithley 3730 is a two pole 6x16 high density matrix card that can connect up to six differential instrument channels to any combination of 16 duts devices under test any row can be connected to the series 3700a mainframe backplane by using the analogue backplane connection relays this allows for easy matrix column expansion a matrix of up to 6 rows by 96 columns can be supported within a single 3706a mainframe with