The tone generated by this bell changes when we press and release the switch. The circuit is from a 1985 Radio Electronics. Some changes can be made to improve its performance.
This circuit was found in a 1992 publication. The circuit uses common components and includes the...
The traditional circuit was taken from a French magazine Radio Plans that no longer exists but can...
The amplifier shown in the figure is characterized by the very high input impedance, given by the...