The voltages in an adjusted range in the trimpots are indicated by 3 LEDs. The LEDs indicate when the voltage is below the range, above the range and in the range.
This Schmitt trigger in current mode for frequencies up to 50 MHz was found in a 1969 Motorola manual....
VR can be from 50 to 220k it is recommended to connect a 100-ohm resistor in series. The lamp may...
This circuit was published in a 1977 English magazine, but remains current, since we can assemble it...