Strange button added to my Model I

[mrthreeplates]

Anyone have an idea what this button was intended for?



Here is how it is wired internally:



I checked with a PEEK, and the button is wired to the last row of the keyboard matrix (same as the shift keys), and returns a 16 when pressed (e.g. bit 4). The shift keys are bit 0.

As far as can tell, this is an unused bit, so I'm assuming this was intended as some kind of function key.

However, I have no idea what it might have been used for or what software might take advantage of it.

Any guesses or suggestions?

BTW: This computer was an Ebay find Model I, so I don't know its history. The other switches I found on the model I are for disabling the lower case kit and a switch to toggle between Level I and Level II ROMS. So, this computer clearly belonged to someone who enjoyed modding.

Thanks for your time!

 

[Eudimorphodon]

The original version of the “Electric Pencil” word processing program required the user to add a “Control” key to the matrix like this if you wanted to use it in lowercase, I’d guess that’s what it is. Sadly it’s one of the cleaner installations I’ve seen.

 

[mrthreeplates]

Thanks! It is really interesting to read about the history. This Model I does seem like it was setup for use with Electric Pencil.

http://www.trs-80.org/electric-pencil-lowercase-modification/

Much appreciated!