What is purpose of the CH button and
CH switch position on the Omron Elite 8002 Taschen-Rechner?
(For those who don't know German, “Taschen-Rechner” just means “calculator”.)
The switch has three positions: ON, OFF and CH. Only in the ON position is the calculator display lit up; in the CH position the calculator apparently does not do anything.
See the linked website for a photo of the calculator. I will provide a better photo later.
I've tried these things to get information about the CH button:
Key in number 123, press CH. Nothing happens. Press again. The VFD shows
Key in 10, press CH (VFD still shows
10.), key in 20, press =. Nothing happens.
Calculate 200+100 (VFD shows
300.), key in 1000, press CH. The result is
According to the last try, it looks like it subtracts the previous value from the currently entered one. (More experiments confirm that it works in this way, as a reverse-subtract.)
So, the question is: What is the “CH” button for (maybe it is in German) and what is the “CH” position of the switch for?
I do not have any manual and I do not have any idea what these “CH” labels could mean. There is also a connector that looks like a 2-pin 3.5 mm jack on the bottom. What is its purpose? Could it be related to these buttons?