13 ms·
It is useful as a perimeter alerting mechanism. A signal mirror (with a hole in the middle) would be the next best thing
by egberts1 2y ago
It is useful as a perimeter alerting mechanism.
A signal mirror (with a hole in the middle) would be the next best thing
- egberts1 2y agoFishing line with two cups on each end makes for an excellent 300’ communication line