The capacitor used in this circuit can have values between 5 and 30 uF. The circuit is of old documentation for radio amateurs. Observe the special source used in the supply.
We found this ultrasonic emitter in a 1964 publication. The transducer is a piezoelectric type....
This 80's circuit has an input resistance of the order of 880 M and gain 10, using operational...
This circuit was found in 1968 General Electric documentation. The circuit uses components from the era...