Why USB C Crushes the OLD USB Plug

The old USB plug topped out at a feeble trickle. The new one powers laptops. Same idea, wildly different limits. Why?

Both carry power over metal contacts. So why could the old plug barely charge a phone while the new one runs laptops?

The old USB-A plug had four pins and no way to talk. With no conversation possible, it played it safe: a fixed five volts at a tiny half-amp, about two and a half watts. USB-C added signal pins that let charger and device negotiate. Now they can safely raise the voltage far higher and pull much more current, reaching a hundred watts or more. Those same pins sense which way the plug is flipped, since USB-C carries contacts on both sides.

Here is the twist: the shape did not make USB-C faster. The real upgrade is invisible: tiny signal pins that let two devices negotiate. Without that conversation, USB-C would be as weak as the plug it replaced.

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