Found in a 1967 General Electric documentation, this meter uses Nixie tubes, popular at a time when LED and liquid crystal displays did not yet exist.
The frequency of this circuit depends on C1 and, for the indicated values, it is 1 kHz. Equivalent...
This configuration with the LM383 appears elsewhere on this site. The circuit shown was obtained...
This circuit was obtained from HAM Radio magazine in an 80's issue. The FETs are types of the time...