The ports used in this ultrasonic remote-control transmitter are TTL, requiring a 5 V supply. The transducer is a piezoelectric type, not very common today.
This circuit was obtained from a Radio Electronics in May 1967. The circuit consists of a system...
This simple two-transistor capacitance meter uses a 50 uA microammeter as an indicator instrument. The...
Found in a European magazine from the 90s, this circuit emits beeps that are several seconds apart to...