And use pathlib to get the suffix.
I think this approach is cleaner.

This allows the code after it to be tabbed back, which I prefer.
Also I changed comments a little.

I think it's good to have this documented.

This makes it more obvious what it's for.

Adjusted some comments, newlines, formatting.
We want to catch it if a queue item is somehow not a correct size tuple, so I'm just doing a generic except instead of excepting Empty.
Variables that end in `sig` now end in `_signal`.
`_read_thread` no longer takes `thread_index`, as it wasn't using it.
Swapped the order of the signal check and try block.
Removed manual unregister of timer, as returning None is enough.

There are multiple threads.
All the other files follow a plural naming scheme.