Found in a 1924 publication, this 2-valve receiver has a speaker output. Power comes from several batteries. Information about the coils is given.
In the original publication of the 90s a 556 consisting of a double 555 is suggested. The circuit...
This circuit was found in a 1966 EEE. The circuit uses transistors from the time but can be made...
This circuit can be used in alarms by activating a relay or a current load that depends on the...