The Covox Speech Thing is an external digital-to-analog converter (DAC) that plugs into the parallel printer port of a PC.

The Speech Thing was introduced on December 18, 1987[1] by Covox, Inc. of Eugene, Oregon, for about US$70[2] (equivalent to $188 in 2023) and priced US$79.95 as of 1989.

[3] People soon started to build their own (DIY) variants, since its communication protocol and DAC is simple and only requires soldering a few cheap parts.

The original Covox plug itself doesn't use sequential logic or a clock signal, so theoretically it can operate with any sampling rate.

The Covox plug couldn't directly substitute any of the popular cards of that age (AdLib, Sound Blaster, Gravis UltraSound, etc.