How did landline phones work during power cuts?
This article explains the technical mechanism behind traditional landline phones, which remained functional during power outages because they were powered by the telephone exchange via copper wires. It contrasts this reliability with modern smartphones that depend on local electrical grids.
Why it matters
It provides historical context on infrastructure design and explains why older telecommunications systems offered superior resilience during emergencies compared to modern digital networks.
The secret lay far away from your home. Unlike today’s smartphones, traditional landline phones did not depend on the electricity coming into your house. Instead, they drew power through the same copper wires that carried your voice. These wires were connected to a telephone exchange, a central hub that linked thousands of telephones together.
The exchange constantly supplied a small amount of direct current (DC) electricity, usually around 48 volts, through the telephone lines. A traditional landline phone needed very little power, just enough to carry your voice and ring when someone called. Because the electricity came from the exchange rather than your home’s electrical supply, the phone continued to work even if your neighbourhood lost power.
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