IMPORTANT UPDATE FOR WIRING!!! See below:

The french always used fancy new tech in their cars. And so they did in the early 80s. Starting with the Renault 25 they introduced a module with the catchy name "Boitier de synthèse de la parole" ... wich translates to "Speech synthesizer box". This first generation of speech synthesizer boxes used a TI TMS5110A speech synthesizer chip in combination with a TI TMS6100 (16k) ROM. The synth is driven by a ST ETL9344 Microcontroller. The rest of the box is just voltage regulation, an amp, and some circuitry to step down the 12v signals from the car to the voltages of the Microcontroller. Its basically a Speak and Spell without Display and 12v wire inputs instead of buttons... Even the construction with the wires connecting the boards together reminds me of the construction of early Speak and Spell Models...

(some Pictures are placeholders linked from the web until i have my devices to take own pictures). 

source : https://www.journaldulapin.com/2021/05/22/synthese-vocale/

The same website also has a wiring diagram... But its french... so i translated it.

This is the wiring for the Phase 2 (facelift in 1987) synthesizer boxes.

IMPORTANT WIRING UPDATE!!! RENAULT MESSED UP THE NUMBERING!!!!! CONNECTOR 2 IS CONNECTOR 3 AND VICE VERSA!!! IMPORTANT!!!!! FOR FACELIFT AND PRE FACELIFT!!!

The "?" are wired on the circuit board to the connector but have no documented function.(Not tested yet). "Number connector (number pin)" is an internal connection from one pin to another pin. The connector 4 in my list is not the ground connector 4 shown in the original documentation! Its the one below connector 1! This connector is unused in the car and not documented.

Here is a thread wich shows the Phase 1 (pre 1987) wiring :

 http://www.renault25.com/data/forum/viewtopic.php?f=90&t=18425&sid=e6c6469d3b42ebd5fda7deaaf8539c39&start=80

Translation: 

The Phase 1 wiring is a little bit different but basically the same.

Another interesting thread is this : http://www.renault25.com/data/forum/viewtopic.php?f=38&t=10546&start=20

Here i found some informations about the RPM Signal and the Speed signal.

Speed is a Squarewave signal from about 12,5 - 13Hz for 10Km/h

RPM is 200Hz for 1000RPM is a Sine. works from 4.5v to 20v.

Because europe is europe and we have a lot of languages here, Renault made several Versions of the Speech synthesizer Box. German, French, English are the ones i can confirm. But i think there are Spanish and Italian versions too...

This is an interesting link to a collection of "all" versions of ROMS that TI made for the Speech synthesizers. 

The French version of the Renault Rom is documented properly. The rest is not...

I have ordered 2 Voice Synthesizers. A german Phase2 Box and a French Phase1 Box.... Lets hope they arrive soon...

I found a link to a page wich shows a very early version of the Synthesizer box from a 1983 Renault 11. It is a single sided PCB with wire bridges... It looks similar from the general layout. That explains the strange use of upper side traces on the newer version. Note the resistor soldered to 2 wire bridges in the center of the picture ( 149 150 ) right next to the right side of the TMS5110. On the single sided variant that makes sense. But on the double sided version that does not make sense to do it like that... But they did not change this detail. I was confused why they did it like taht... Now i know... its a relict from a single sided board... Isnt it amazing what we learn here? 

http://www.silicium.org/forum/viewtopic.php?f=32&t=35310&sid=5c08ab1f1d69b4e5e6a4f994be5b39e4&start=30

Here you can see that the french Rom "CM62188" was used as early as 1983 (the wiki says 1986). Wich makes it a Phase 1 part.

ThisThis picture also told me that there is a Philips TDA1020 Amplifier (below the fat blue capacitor). This is a Car Radio Amp... Im not sure if in the early 80s dedicated parts and chips just for cars already existed. But i know that Philips made a lot of in car entertainment for Renault back in the days.

Maybe i can mod a volume control into the fixed circuit, or a line out ... Im still not sure if i should mod these parts... They were quite cheap to buy for me, but that does not mean they are not quite rare, especially the german version i bought...