Found in a 90’s Popular Electronics, this circuit uses two CMOS inverters to generate a signal of a few hundred hertz determined by C1 and the R3 setting.
We found this configuration of band rejector filter or band rejector with operational 741 in a...
We found this circuit in an old European documentation, but the components used are still all...
We found this transmitter for the 70 to 90 MHz band (FM in Japan) in a Japanese publication at the...