Manufacturer:  Honeywell / Schneider Model:  Digitest 500 Year:  1969 Schematic:  RE

Functions:  DCV, ACV, Ohms Display:  NIXIE Digits:  3 Logic:  discrete transistor, LSI

A funny little VOM built into a calculator-style case. The matrix organisation for the function/range selection is novel.

This is actually a Schneider product made in France, re-badged for sale under the Honeywell name. The model was also sold under the Schneider name. The Schneider units seem to be more prevalent, at least in Europe, based on web searches.

A single IC contains most of the digital portion of the electronics - the counters and display multiplexing circuitry - a fairly high level of integration for the time. A single 709 op-amp is also present, the rest of the circuitry is discrete, albeit with several special multiple-resistor ceramic modules.

The unit can be operated from both the AC mains or an external 12 VDC supply (tip negative on the DC barrel connector). The AC mains supply can be configured for 100 to 240VAC, the selection being made by solder connections on the bottom of the main circuit board.