The Mini-B was adopted, originally, for much smaller devices, like cameras, as USB started actually becoming “universal” and consumers didn’t want to deal with legacy ports any longer. It has the exact same two signals, power, and ground that you find on Type B connectors. And while a Type B connector was only rated for 1,500 plug/unplug cycles, the Mini-B was rated for 5,000 cycles. Another thing that was added in the Mini-B generation was USB On-the-Go. USB was designed as a pure Host/Target protocol. A host device — your PC — can talk to up to 127 target devices per port (via hubs, of course). But targets can’t talk directly to targets. That was fine when your PC was talking to a mouse or keyboard, but what about a PDA or Smartphone? That’s a computer in its own right, but also has good reason to hook up to a PC via USB. So On-the-Go added one more signal, which allowed the port to decide to be either a Host or a Target. That still didn’t fundamentally change USB.
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