For the Voice display circuitry, it took me some serious thinking until I realized that it was infact just a 10 segment LED VU meter. If you take this one VU meter and mirror it to both the left and right sides (starting with the forth segment of the center bar) and do a complete mirror of the top to the bottom you have a device in which operates just like the voice box in the TV series, pretty cool I thought. So I scoured the net to find a circuit of a VU meter. I found one that ran off a single chip. If you were to add amplifying transistors to the output of this chip you can run the 2-6 LED's that are on at any one time in the voice display. I built it and it worked absolutely perfectly. Below is the schematic I made from my experiences.....
NOTE: To prevent any damage to the circuit from a automotive electrical system I added a 12v 1 amp voltage regulator to the positive side of the power input, it may not be necessary but I wanted the protection.
NOTE #2: You will need to use the audio transformer , if your going to run this off your car radio.