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.
The critical components of this 1978 circuit are transformers, which, hopefully, can be obtained from...
This circuit was found in a 1995 documentation, consisting of a car protection system that blocks...
Suitable for dual applications, this timer was found in a 90s Popular Electronics. The circuit...