The Sprayberry Academy of Radio VOM tester was part of the lessons taught by correspondence by Sprayberry. The R X 1, R X 10, and R X 100 settings need a 7.5 volt battery source. The set used a battery with screw terminals.  The R X 1000 setting requires connecting a 45 volt battery.  The 1 mA draw at full-scale indicates a 1000 ohms-per-volt meter. 

The VOM tester includes a resistor-capacitor substitution box also built inside the case for in-circuit substitution by way of the two banana jack/ binding posts on the right. 

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Elenco delle radio e altri apparecchi della Sprayberry Academy of Radio; Chicago, IL