This amplifier is from a 1990s Linear Technology component manual. The circuit requires symmetrical power supplies.
This is a possible circuit for the receiver of the previous circuit. Other circuits can be found...
February 25, 2015 - Mouser Electronics, Inc. today announced their new Robotics Technology site....
Of course, the range of this transmitter found in a 1992 documentation is not exactly 4 km, as it...