We found this circuit for video games in a Radio Electronics magazine from August 1977. The transistor can be any common RF type that reaches the desired signal frequency.
The quiescent current of this alarm is in the order of microamps and the same is true for the...
This circuit is from a 2005 Linear Technology publication. It converts current into load sensing...
This circuit can operate in a 100 dB range with signals of up to 100 MHz frequencies. Similar...