[ARC5] Reverse engineeing the BC 456

[Robert Nickels]

While electret capsules are dirt cheap (like a dime), it's impossible to 
go wrong with these pre-assembled amplified electret mic boards, which 
can be found on eBay by searching for "Arduino mic":

http://www.ebay.com/itm/1x-Electret-2016-LM393-Microphone-Sound-Sensor-Detection-Module-for-Arduino-/322200269530

They're a buck apiece if you're willing to wait, or $5 from statesite 
sellers if you're in a rush.  Sound quality is excellent and they will 
put out 5 volts of audio with the on-board gain control wide-open, and a 
good fraction of that even when driving a low-Z load (47 ohm resistor).

The above is just a typical listing picked at random - but all the 
similar parts seem to use the LM-393 dual comparator in an op-amp 
configuration.

73, Bob W9RAN