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.
We found this circuit in the Texas Instruments opto-electronics manual. The button resets and the...
This circuit uses an integrated hard to find today and the phone must be of high impedance. We...
Any general-purpose transistor can be used in this circuit that generates a rise ramp that can be...