USB cables
The cables which the USB committee specified were designed to support a number of USB's underlying goals, and to reflect lessons learned from the varied menagerie of cables then in service. In particular:
- The cables are designed to be robust. Many previous connector designs were fragile, with pins or other delicate components prone to bending or breaking, even with the application of only very modest force. The electrical contacts in a USB connector are protected by an adjacent plastic tongue, and the entire connecting assembly is further protected by an enclosing metal sheath. As a result USB cables can safely be handled, inserted, and removed, even by a small child. The encasing sheath and the tough moulded plug body mean that a connector can be dropped, stepped upon, even crushed or struck, all without damage; a considerable degree of force is needed to significantly damage a USB connector.
- It is difficult to incorrectly attach a USB connector. cables cannot be plugged-in upside down, and it is clear from the appearance and kinesthetic sensation of making a connection when the plug and socket are correctly mated.
- The cables are particularly cheap to manufacture.
- The cables enforce the directed topology of a USB network. USB does not support cyclical networks, so the cables from incompatible USB devices are themselves incompatible. Unlike other communications systems (e.g. RJ-45 cabling) gender-changers are never used, making it difficult to create a cyclic USB network.