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Covox Voice Master Key

This item came up on eBay a long time back and went straight into the 'projects' box. Thanks to a newfound push to clean up the spare room, that box has been turned upside-down and dealt with. So, without any further ado, I present to you a 1988-vintage COVOX Voice Master Key.


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The box was well-worn, but all text can be read. Of interest is, in the second-last paragraph, the redacting of the quote "Plays back through optional COVOX Speech Thing". Was the redaction done by a child with a marker? Or from the factory? Finding information on this card online is pretty difficult. First hit was this Korean blog post on and you'll notice that the redacted sentence is totally removed from their version of the product. Their version seems to be a lot newer, but only of box design, not product name or quality.

Nerdly Pleasures also has a post on COVOX devices, but was very light-on for info on this card. I hope I can help them with their photo of the card as well. Also, the I/O for the DAC can be gleaned from the jumper setting above.

So what does it do?

First and foremost, this is one of the first pieces of hardware to let you control an IBM PC via voice. If I had the software, I'd test this functionality out... unfortunately I don't and no amount of searching has dredged up the installation disks. There's a disk image listing here, but no actual disk image? I messaged the author of that post and he just silently stepped out of the conversation... he must have the actual image to take those screenshots from DOSBOX? I then started by own thread, but no one cares.

A little more digging brought up this request post on Amibay for the same software. I posted a bump reply and got in trouble for hijacking someone else's thread... didn't realise that was a rule. I then PM'd the author, but no response as of yet.

So, without any software, I can't do the voice recognition/control stuffs... but can it play audio?

Audio output hardware

This unit does have an output port and the included head-set is just that; a speaker and a microphone! There are two microphone ports on the card, but we don't actually care about them as we don't have any software that'll make use of them. The headphone port interests me though as, with the redacted text on the box, there must be some way to use the 'included' COVOX Speech Thing functionality. The directory listing of the installation disk above even has a THING.EXE which must enable this card as a sound output device.

The output circuit includes an LM386N amplifier that's fed from the resistor bridge. That bridge is fed directly from the ISA bus data lines, so it must do something if data is fed in. The I/O Address jumper selections allow settings from 0x22f through to 0x28f. I initially thought that was 0x0220, thinking the F was just some naming style, and, after taking out my SB16, tried to get my machine to output sound via FT2 on 0x220... this was entirely fruitless and entirely wrong! I mean, come on, the jumpers don't lie... the I/O ranges really are all based with an 'f' on the end!

So, what to do? First up, anything that wants to use a COVOX Speech Thing as a sound output device will expect it to be on LPT1 or LPT2. These ports are configured via your BIOS and, well, it just wont work adjusting BIOS settings as anything configured there will just send data out the existing configured printer port. I went googling around and found that people had built their own DACs back in the day and someone even has a project for a DAC that sits in an ISA slot known as ISA-DAC-r0. Further on from that, I then found instructions on how to use it on the DOS Re-loaded forum.

There's a really interesting screenshot half-way down that forum topic where the user has used the DOS debug command to hack a memory address. This address contains the I/O register of your machine's LPT ports. Hilariously, you can actually tweak these addresses live when your machine is running!? The basic idea is to type debug, hit enter, then type the following:

-e 40:08 78 03 2f 02

then press enter and then type q and enter to quit. Above, you've entered the bytes 78 03 2f 02 into memory address 40:08. It turns out that that memory address is the system configuration area for the IO base address for your LPT ports and you can chain as many as you want together to pretend you have LPT ports. In the case above, the first port is 0x378, written as high-byte low-byte and then 0x22f, again as high-byte low-byte. Entering the command above will configure your DOS session to have LPT1:0x378 and LPT2:0x22F. Does it work? I configured Fast Tracker II to have a SoundPlayer on LPT2...




Actually... here's a proper demo of its capabilities:

Woah! The audio quality was as-good-as any original SB2.0 that I remember... but it's probably worse... and MONO. Seems can you have two DACS and have FT2 run LPT1+LPT2 for stereo sound. More games were downloaded and tested and all worked fine! Amazing.

Now to just find the actual software!

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  1. You may ask youtubers: LGR, Adrian Black, Tech Tangents, Vwestlife, Mr Lurch.

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