Photo credits

Every photograph on Open Line is free to reuse: twelve are dedicated to the public domain under CC0 and one is in the public domain. We found them on Wikimedia Commons, several of them originally published on Unsplash, and link each one to its file page below so you can check the author and licence.

Photos illustrate a topic; they are not evidence. Any people or hands shown are models or passers-by with no connection to the subjects, organisations or situations discussed on the page, and no product, brand or venue is endorsed.

Photos by page

• Home page (top): Three vintage pay telephones with rotary dials and coiled cords mounted in a row on a pale wall. Photo: Pavan Trikutam / Unsplash, via Wikimedia Commons (CC0 1.0).
• What is VoIP? How a phone call travels over the internet: Dozens of blue, yellow and green network cables plugged into a rack-mounted Ethernet switch. Photo: Raysonho (Open Grid Scheduler / Grid Engine) / Wikimedia Commons (CC0 1.0).
• Wi-Fi calling explained: how it works and how it differs from calling apps: Two hands holding a smartphone over a café table with a magazine and two cups of coffee. Photo: Maliha Mannan / Unsplash, via Wikimedia Commons (CC0 1.0).
• Why VoIP calls break up: latency, jitter, packet loss and how to fix them: Over-ear headphones lying on a dark desk beside a smartphone with a lit screen. Photo: wu yi / Unsplash, via Wikimedia Commons (CC0 1.0).
• How much data does a VoIP call use? The calculation, codec by codec: A hand holding a smartphone whose screen shows a grid of colourful app icons. Photo: bohed (Pixabay), uploaded by Océanos y dados / Wikimedia Commons (CC0 1.0).
• VoLTE and the 2G/3G switch-off: will your phone still make calls?: Aerial view of a lone mobile phone mast beside a country road, surrounded by green fields and a farmhouse. Photo: Wikideas1 / Wikimedia Commons (CC0 1.0).
• Calling abroad: roaming, local SIMs, eSIMs, Wi-Fi calling and apps compared: Close-up of an airport departures board listing destinations, departure times and flight numbers. Photo: Redolta / Wikimedia Commons (CC0 1.0).
• EU roaming rules: what "roam like at home" covers, and what it does not: A blue European Union sign marking the Slovenian border beside a road that passes under a bridge. Photo: Dantadd / Wikimedia Commons (Public domain).
• eSIM explained: how it works, which phones support it, and using it abroad: Diagram of SIM card formats from largest to smallest: Mini SIM, Micro SIM, Nano SIM and the tiny embedded eSIM chip. Photo: Jbond2018 / Wikimedia Commons (CC0 1.0).
• Keeping your number: porting, caller ID and spoofing when you call over the internet: Close-up of an old rotary telephone dial with a paper number card at its centre and a coiled cord beside it. Photo: Daria Nepriakhina / Unsplash, via Wikimedia Commons (CC0 1.0).
• Emergency calls over VoIP, Wi-Fi calling and apps: what works and what does not: A blue roadside call box sign on a pole with a small solar panel, beside a desert highway. Photo: Ruff tuff cream puff / Wikimedia Commons (CC0 1.0).
• Supported devices: what makes a phone work well (or badly) for internet calls: A smartphone with a dark screen lying flat on a pale woolly blanket. Photo: Astra.L / Wikimedia Commons (CC0 1.0).
• What calling and messaging apps actually encrypt (and what they still reveal): Three padlocks on a table: a brass key padlock, a brass combination lock and a small red combination lock. Photo: Mx. Granger / Wikimedia Commons (CC0 1.0).

Each photo is stored on this site in two sizes, cropped to a 3:2 frame and converted to WebP; nothing else was changed. If you are the author of one of these images and believe it is credited wrongly, please contact the publisher listed on the legal notice.