This is a dynamic audio compressor which outputs a constant audio level and can be used for FM transmitters too. It uses a preamplifier with TDA 1054 produced by SGS-ATES. IC1a is a preamplifier stage with a total gain of 50 (1 + R5/R4). IC1b is connected as a amplifier stage with a 400x gain (1 + R11/R10).
The audio compressor power supply has 9V.