Teletype in

When I read ‘in’ on my teletype I get random values between 7 to 72 when no signal is connected. Is that noise normal?
I can get a stable 0 by applying a small negative DC voltage to the input.
Another weird thing is that I can get values like 16 when I do a
QT IN 1000
I’m expecting 0, 1000, 2000, 3000…
That behaviour seems to be related to the loaded scene. Best test case is “Triangle Mountain”.