This circuit reproduces the dial noise in a small speaker. The transistor can be a general-purpose type. We found it in an 80's Electronic Design.
Using a 555 this circuit was found in old documentation, but it is still valid. | Clique na imagem...
This circuit was obtained in a 1976 magazine. We can use the 555 and another BC548 to generate square...
The circuit presented here shows how two flip-flops of a 4027 can be connected to perform a...