This small transmitter appeared in the March 1989 issue of Radio Electronics magazine. The two-transistor circuit used an electret microphone and had a range of a few dozen meters.
This decoder TTL circuit for 15-channel remote control was found in Selezione Radio, Italian...
This is the circuit of a sensitive voltmeter using a difficult-to-obtain 5 uA full-scale...
This circuit compares two light intensities, providing the indication on an analog instrument. The...