This circuit was found in RCA documentation from the 1980s. The circuit uses LDRs of the time and the 50 uA instrument has zero in the center. R1 and R2 may have 2k2 and R3 10k typically.
This 7400 TTL circuit has a memory, keeping the LED on when a pulse is detected. The circuit must be...
This dual-LED circuit indicates three signal levels. It was found in the January 1996 issue of...
This circuit measures the RF power of oscillators and small transmitters in the range of 0.05 to...