We found this code key or coded keyboard in a publication from the 90s. The circuit uses components that are still common today and is powered by a 12 V voltage according to the relay used.
Found in a publication for radio amateurs from the 1990s, this circuit makes it possible to...
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This simple transistorized receiver with earphone was found in a Japanese publication from the...