More old #electronics equipment from my Ebay-enabled home lab. #NixiTubes! This 1969 #Keithley 615 #electrometer has a discrete MOSFET front-end and a dual-slope A/D made of gate-level RTL chips. The rear-panel parallel output is labeled PRINTER, because that is all you were likely to do with it in 1969. I once used it to measure the beam current of a Philips #electronMicroscope. Here it is getting the right answer for a #Victoreen 1 GΩ resistor.