The Odyssey2 had two optional modules: a voice synthesizer, called “The Voice,” which was only released in the U.S.; and a chess module, which carried a (then) powerful microprocessor, the Z80 (actually a National Semiconductor NSC800, which was a clone of the Z80), had 2 kB of additional memory, and was only released in Europe. Both were to be placed on top of the console, using the available cartridge slot.
The voice synthesizer module had a slot for you to be able to install the game cartridges, and the games had to be compatible with it in order for it to work. In some games, such as Attack of the Timelord! and K.C.’s Crazy Chase!, the module would really speak (“run!,” “go!,” “incredible!,” and “oh, no!” were some of the phrases available on K.C.’s Crazy Chase!, for example), while in others it would either bring additional sound effects (e.g., Killer Bees!) or background music (e.g., Turtles!). We posted several videos on the “Playing with the Odyssey2” page, where you will be able to hear the sounds produced by The Voice.
One drawback of The Voice was that the sound came out of the module itself, not through the TV speakers. Because of that, the module had a sliding volume controller that work independently of the main sound generated by the console.
In Figure 13, you can see what the voice synthesizer looked like inside.
The main chip of the voice synthesizer is a General Instruments SP0256-019 speech chip. This chip has 2 kB of internal ROM containing the sounds and phrases the module could say, and it loads more phrases from an external SPR-128-003 speech ROM. These phrases could be ready-made words such as “incredible!,” “run!,” and “great!”; they could be phonemes to be combined to form new words; or they could be special effects sounds.