USB connector

Types

USB connector types multiplied as the specification progressed. The original USB specification detailed Standard-A and Standard-B plugs and receptacles, then referred to as simply Type‑A and Type‑B, then as other Type‑A and Type‑B connectors were added (first Mini, then Micro), the terms Standard‑A and Standard‑B were applied to the original connectors. The A–B distinction is to enforce the directional architecture of USB, with only the host and hubs having Type‑A receptacles and each peripheral device having a Type‑B. The data pins in the standard plugs are recessed compared to the power pins so that power and grounding is established before the data conductors are connected, and the reverse when unplugging. Some devices operate in different modes depending on whether the data connection is made. Charging docks supply power and do not include a host device or data pins, allowing any capable USB device to charge or operate from a standard USB cable. Charging cables provide power connections but not data. In a charge-only cable, the data wires are shorted at the device end; otherwise, the device may reject the charger as unsuitable.