This circuit was found in the September 1971 Radio Electronics magazine. The buzzer can be replaced by a relay according to the supply voltage. R1 adjusts the sensitivity.
This medium wave commercial receiver from the 1960s was found in a Japanese publication at the...
We found this circuit in a 1967 Electronic Design. The circuit used a MOSFET of the time, which is...
This step of two transistors has a high input impedance due to the use of FET. We can use BF245 for...