[Coco] Source for CoCo cassette cable, or components to build one?

[Allen Huffman]

> On Feb 9, 2015, at 2:54 PM, Chris Osborn <fozztexx at fozztexx.com> wrote:
> 
> CoCo cassette cables will work with the TRS-80 Model I, the MC-10, the Model 100/102, original IBM PC, and PCjr. too.

I saw original PCs (with cassette port) at the college I went to (around 87) which was the first time I ever got to verify they started out with cassette ports :)  Where did this standard originate? Did something have it before the TRS-80 Model I? I never realized that the PC copied the TRS-80s :)