This circuit was found in a Ferranti documentation from 1969. The transistors are common types of the company at the time. Smaller equivalents may be used. The output power is of the order of 150 mW.
In the figure we have a way of receiving ultrasonic signals of a single frequency using a PLL 567....
The HA2620 integrated circuit used in this comparator is from the 80's, but the setting can be...
The UM3562 integrated circuit (not very easy to find) synthesizes three types of sound that...