Low Voltage Test (CB22158E)

This is a simple voltage tester for voltages from about 2V to about 15V with the indicated resistor and red LEDs.

Turntable Preamplifier (CB19172E)
This RIAA equalizer preamp was found in a 1990s schematic. The transistors are an old version of...
Battery Status Indicator (CB15852E)
This circuit uses two LEDs to indicate the state of a battery, the voltages at which they...
AC Motor Control (CB12330E)
The bridge diodes of this circuit, found in a 1967 publication, are according to the motor...