High performance wireless microphone

Circuit working principle: This circuit uses the FM special integrated circuit
BA1404 device , omitting the stereo encoding circuit, and the circuit is very simple.
The microphone uses an electret microphone. Due to its non-directional nature, it is very easy to self-excite during use
. For this purpose, two microphone heads are used, one for source amplification and one for drain amplification
, which are connected to pins 1 and 18 of BA1404 respectively. There are two symmetrical
amplifiers inside BA1404 , which are amplified and mixed and output from pin 14.