A Building’s Fire Phones 🔥 📞

[DarkRange55]

These are still required in US buildings. It's a very, very old technology and is very vulnerable to compromise. Any kind of ground fault or anything kills it. I've seen this entire system downed in a building because of a gum wrapper. Not joke. The circuits are all wired in parallel. Sound Powered Phones which is what ships in WW2 used. They operate on magnetostrsiction.
Quartz crystals exhibit piezoelectric properties, meaning they can generate an electric charge in response to applied mechanical stress (such as vibration). In some parts a building, radios and phones aren't always reliable. Its a backup communication system for firefighters

Sound-powered telephone - Wikipedia

en.wikipedia.org

Magnetostriction - Wikipedia

en.wikipedia.org

 

[Uninfluential_Karma]

Despite living in the US my entire life, I've never noticed these or heard about them. I really liked learning about them, thank you for posting this!

 

[DarkRange55]

Despite living in the US my entire life, I've never noticed these or heard about them. I really liked learning about them, thank you for posting this!

They can be more often than not in back service corridors, service stairwells, back hallways, ect. Usually in parts of the building with heavy shielding (a lot of steel and cement to absorb radio signals).