One commdot is temporarily affixed to the scalp just behind the ear; another commdot is stuck to the throat just above the Adam’s apple. The microelectronics in the dots can transmit and receive for a distance of only about a meter, but this is far enough to put the dots in contact with a large, more powerful device. One can thus use a communicator or hand computer and still keep both hands free for other tasks. Commdots are powered by ultraminiature superbatteries and can be tuned by another device. Most communicators support this tuning capability.
When one desires to communicate over more than one frequency at a time or to operate more than one device, a commdot multiplexer is used. The multiplexer is a small box worn on the belt and coordinates activity between the commdot and several electronic devices. The operator can then receive or transmit only on the channels desired, and he can turn signals on or off at will.
The commdot is a natural step in the evolution of communications interfaces. Wired headphones with speaker first appear around TL–5, and continue to decrease in volume as speakers and microphones improve. The first wireless headphones appear around TL–7 but do not become common until TL–9 when the batteries have improved sufficiently to increase the operational time between battery changes. Speakers are nearly eliminated as bone conduction is used with the advanced prosthetics available at TL–12, the commdot starts to become an implanted device for covert operations. By TL–14 it is possible to power the internal communications prosthetic using a glucose-powered fuel cell that extracts the fuel from the bloodstream for continuous operation. While rare, some advanced systems have incorporated IFF and emergency beacons into the implants to enhance their operational usefulness.
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