We installed a perminent lightning warning system at a public park years ago. It consisted of a 20"x20"x4" panel requiring a 120 volt dedicated circuit. It came with a pole mounted antenna with a ball on top. It had battery backup capability for power failures. It had an optional automatic dialer which require a telephone line and a set of dry contacts NO and NC for the alarm device. We did not purchase the equipment, the community did and we installed it at no-charge. We connected a loud horn made by Edwards with a timing relay which could be heard throughout the facility. I was suprised how sensitive it was, it sensed the danger of lightning way before you saw any indication of an approching storm.