This interesting circuit, from a digital documentation two years 1978 shows how to implement a circuit that measures the position or angle of a stepper motor controlled by a microcontroller.
This transmitter has a power of only 2 W, but with a good antenna it can send its signals over...
The modified Hartley oscillator seen in the figure can generate signals ranging from 3 MHz to 10...
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...