This is a Japanese commercial radio from the 60s. The superheterodyne circuit of 7 transistors for medium waves has 200mW of output when powered by 4 common batteries.
Using an integrated circuit that was available at the time, this circuit produces animal sounds such...
The idea of this circuit is to obtain a resistance of 10G ohms using an operational amplifier....
This circuit, when it picks up a sound, emits a beep and records for a while the sounds picked up by a...