We found this circuit in a Hands-On Electronics from the 90s. The circuit must be connected to an external amplifier. Frequency control is capacitive, using an antenna for this purpose
This amplifier for hearing aid was found in a 1968 documentation using an integrated of the time....
We obtained this circuit from a 1993 documentation. The circuit has 9 current ranges that are...
In the figure we have the transmitter of a data transmission system with optical fiber suggested by...