The latest acquisition is the JE520 by Jameco. This external voice synthesizer came in two variants: the JE520-CM for Commodore and JE520-AP for Apple II. The only difference was the interface connection to the computer. The Commodore version, the one I have, connects to the user port while the Apple II version connects via an interface slot card. Otherwise, I believe the rest of the hardware to be the same. I found an advertisement for it in RUN issue 7 1984— it retailed for $115-$150.
It’s based on the National Semiconductor Digitalker 54104 voice synthesis chip and four 2764 64kbit (8kbytes) EPROMs that form that vocabulary that it’s able to speak. This means it’s able to speak only using a fixed wordset. National also sold a series of vocabulary ROMs with the chip, but I believe this version has a custom ROM set from Jameco. It includes a built in amplifier and speaker with volume adjustment (located below) as well as a mini jack for sound output. Power comes directly from the computer.
I didn’t receive a manual or software so it’s trial and error. At first, I assumed it would communicate with the computer over a serial interface since most devices that connect to the user port on a Commodore would use serial. And it would greatly simplify communication by using serial. But loading a terminal program resulted in the synth talking complete gibberish.
I later realized that it must be using parallel instead. And indeed, it does appear that way. The computer interfaces via parallel directly to the data pins of the Digitalker chip. On the Commodore, this is PB0 through PB7. So, it should be a simple matter in BASIC to get it to speak. So I tried the following program.
10 POKE 56579,255:REM PB0-PB7 OUTPUTS
20 FOR I = 0 to 255
25 PRINT I;
30 POKE 56577,I
40 FOR J = 1 to 350:NEXT J
50 NEXT I
After RUNing the program, the voice synth began speaking words after iteration 8 with “FAIL”, “FAST”, “FIRE”, “FIRST”, “FORWARD”, etc. (0-7 were silent). It kept speaking properly until iteration 127 when it began talking mostly gibberish again through 255 with an occasional “SECOND”.
I’ve found online that two folks have said that their ROM #2 has gone bad so I decided to dump them in the hopes that I have a good copy. Dumping ROM 1 went well, but ROM 2 seems like it’s going bad. It returns different data each time it’s read. ROM 3 and ROM 4 read fine. So, it appears I also have the same problem most others do. I’m hoping that someone reading this will have access to the ROM set so I can burn a good version and get the voice synth working properly again. I’d even like to try the original National Digitalker Voice Vocabulary ROM set as I’m thinking they should be compatible as well. Leave a comment if you’re able to assist.
An interesting bit of trivia about this device is it has origins that can be traced back to someone named Forrest Mozer. The chip even contains his last name on the top. Mozer was a co-founder of Electronic Speech Systems (ESS) and developed the lossy codec that’s used to encode the speech that’s stored on the ROMs. Apparently, he did most of the encoding himself, by hand! Mozer’s codec went on to give speech to C64 games like Ghostbusters and Impossible Mission, without additional hardware. The National 54104 Digitalker was also used in the arcade hit Berzerk.