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, from the 90's, is intended for operation with vinyl record players of the time, as...
Using a zener diode it is possible to change the linearity of the scale of an analog instrument by...
Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime...