Phone circuit (CB8709E)

With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a basic intercom.

Source Follower (CB6153E)
This stage for JFETs was found in a 1965 US publication, but is valid for modern components. |...
Band Pass Filter 741 (CB13324E)
This traditional configuration of bandpass or bandpass filter with operational 741 was found in a...
Divider by 8 4013 CIR2912S CB16058E (CB16058E)
With 3 flip-flops (which correspond to 1 integrated and a half) we can also make a divider by 8,...