Conductors Without Connectors

By Peter Coffee  |  Posted 2003-11-10

When people say "wireless," they usually mean infrared or radio for connection over distance. The capacitive coupling used by IBM, in its Collective Intelligent Brick storage prototypes, is wireless, but it is not for remote control. CIB depends on actual contact between the faces of stackable enclosures.

Capacitive coupling lets engineers push an electrical signal through a glass windshield, for example, so an antenna can be mounted on a car without drilling a hole. It also arises, whether or not its wanted, when two electrical conductors run close to each other with only a thin layer of insulation between. At any instant, electrons are pushed toward one side of the barrier by a driving voltage; that excess drives electrons away from the other side, creating a momentary current flow until the system comes into balance. If a signal oscillates rapidly enough, the systems tendency to oppose the flow of current becomes smaller.

Its obvious that this can work with something as simple as a radio signal going to an antenna. Its not as obvious how this approach can accommodate the complex signals handled by parallel data interfaces such as SCSI, with their correspondingly bulky connectors and multiwire cables.

What completes the picture are serial protocols like FireWire, which use inexpensive processing power to achieve high data throughput over a simple electrical path. Look to this continuing synthesis to provide simpler, more reliable devices at many points of the IT stack.

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