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 is from a Radio Electronics from 1950. The transistor was still new and called a...
The circuit is from a Radio Electronics magazine from October 1987. The Triac must be equipped with a...
This 1968 Hughes circuit uses period components and operates at 8 Hz. Current equivalent...