This circuit was found in an ancient American documentation. With it is possible to double the frequency of a transmitter For the range of 6 meters obtaining 8 W. The circuit makes use of varicap.
This humidity alarm, rain or leakage was found in a 1992 publication. The sensor consists of a printed...
This circuit can be made usng the TIP32 transistor but must use carbon microphone (not very common these...
This circuit uses in operational amplifier to produce square and triangular low frequency signals....