This General Electric circuit is from the 80's. The PUTs used in this meter are not common components today.
This circuit was published in Popular Electronics from the 90's. The components are common, as...
This circuit is from a 1982 documentation. It can be modernized using LEDs in series with 470 ohms...
The CMOS 4046 integrated circuit is not very common today, consisting of a very efficient PLL for...