The Haʻikū Stairs, also known as the Stairway to Heaven or Haʻikū Ladder, is a steep hiking trail on the island of Oʻahu. The trail began as a wooden ladder spiked to the cliff on the south side of the Haʻikū Valley. It was installed in 1942 to enable antenna cables to be strung from one side of the cliffs above Haʻikū Valley to the other. A building to provide a continuous communication link between Wahiawā and Haʻikū Valley Naval Radio Station was constructed at the peak of Puʻukeahiakahoe, elevation about 2,800 feet (850 m). The antennae transmitted very low frequency radio signals from a 200,000-watt Alexanderson alternator in the center of Haʻikū valley. The signals could reach US Navy submarines as far away as Tokyo Bay while the submarines were submerged.

In this photo provided by Greenpeace, clothes are left to dry on a typhoon damaged tree in Surigao City, southern Philippines on Monday December 20, 2021. The governor of a central Philippine province devastated by Typhoon Rai last week pleaded on radio Tuesday for the government to quickly send food and other aid, warning that without outside help, army troops and police forces would have to be deployed to prevent looting amid growing hunger. (Photo by Jilson Tiu/Greenpeace via AP Photo)

(L to R) British model Leomie Anderson, English singer and television presenter Rochelle Humes, British television presenter from Blackburn AJ Odudu and English television, radio presenter and DJ Maya Jama attend the GQ Men Of The Year Awards in association with BOSS after party at The House of MOTY on November 16, 2022 in London, England. (Photo by David M. Benett/Dave Benett/Getty Images)

A farmer seen harvesting his crops while Mount Sinabung spewing out volcanic ash on July 4, 2017 in North Sumatera, Indonesia. The increased volume of lava dome that reaches one million eight hundred cubic meters, said volcanologist, through radio communications, do not dampen the activities of the people around sinabung, such as farming, harvesting their crops, picking up objects that are still left behind, or just take a picture while walking around near mount Sinabung. (Photo by Sabirin Manurung/Pacific Press/Barcroft Images)

British television and radio presenter Maya Jama attends the GQ Men of the Year Awards at Tate Modern on September 5, 2018 in London, England. (Photo by Splash News and Pictures)

A member of staff prepares herself a crisp sandwich in the Simply Crispy sandwich cafe in Belfast, northern Ireland January 12, 2015. The sandwich shop which opened on Monday is the world's first crisp sandwich cafe, local media reported. The idea of a crisp sandwich cafe started as a joke article on a website called Ulster Fry. The hilarious piece poked fun at recent ridiculous foody trends like the cereal café that opened in London last year. What was once a satirical joke has now become reality, after Belfast cafe owner Andrew McMenamin decided to make it happen. Customers will be able to choose their bread and crisps and add cheese or ham to their sandwich, which will be served with soup and chips. (Photo by Cathal McNaughton/Reuters)

Luis Hernan was always curious about how wireless technologies like radio are transmitted through the air. So after finishing up his studies in architecture, computer science, and design, Hernan decided to research these invisible signals through a PhD at Newcastle University. Hernan set up a system that turned the wireless signals around him into colourful, ghostlike images using long-exposure photography, allowing people to see the strength of the signals around them. (Photo by Luis Hernan)

A visitor relaxes in a sleeping module at Tokyo's tube Hotel “Capsule Inn Akihabara” on February 6, 2007 in Tokyo, Japan. The two-square-meter sleep modules are equipped with a TV, Radio and Wireless LAN and are priced at 3500 yen per night. Uptil recently it has mainly been the office workers who stay at such tube hotels when they cannot go home, but recently they are attracting many foreign travellers due to their Japanese style. (Photo by Koichi Kamoshida/Getty Images)