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 audio circuit was published in a Rado Electronics issue from October 1963. The transistors are from...
This circuit was found in a 1994 documentation. Its signal is applied to any small integrated...
This shield circuit can be used in several applications that involve a feedback signal. The...