This circuit was found in old documentation, however the components used are common today. The selection of times is done by switch and the 556 consists of a double 555.
We found this circuit in a Popular Electronics of the 90s. The MOSFET can be of any type,...
In fact, the correct name would be a hearing aid amplifier. However, we use the name of the...
This circuit controls a relay causing it to open and close its contacts at a speed that depends on the...