Frequency Counter using Obsolete Beam-X tubes

This instrument was made long ago but is still on my workbench and it works, although my Tektronix digital oscilloscope is easier to use to measure frequency and period, but with less precision.

It has 6 decade counters using now-antique Burroughs Beam-X tubes which use magnetic rods in a vacuum tube to count to 10. Since this only worked to 110 KHz, I added a divide-by-ten using a IC when this became available. The Beam-X tubes directly drive NIXIE tubes for display.

It measures frequency, period, interval, stopwatch and ratio of two inputs.