Search Results for: Electrical apparatus used for switching electrical circuits
hundreds of miles, as in the fort-to-fort network used for the geronimo campaign. it was very portable, did not require any power source, and was relatively secure since it was invisible to those not near the axis of operation, and the beam was very narrow, spreading only feet per mile of range. however
, anyone in the beam with the correct knowledge could intercept signals without being detected. [ ] [ ] in the boer war , where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam. [ ] in some other circumstances, though, a narrow beam made it difficult to stay...
https://en.wikipedia.org/wiki/Heliograph