Function unknown_rings 

pub(crate) fn unknown_rings(config: &Config, hours: bool) -> bool

Whether the call screening lets a number nobody knows, or a hidden one, ring at a moment by itself (off, outside its hours, its rules), work or admin time then or not (hours): the phone’s modes then let anyone’s call through, so that nothing it lets ring is silenced (attention::Phone::unknown). Expecting a call is said apart (attention::Now::through).