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Universal Asychronous Receiver / Transmitter. The UART is the controller for the serial devices attached to a host device, such as a wireless module. "Universal" refers to the fact that the device's baud rate and other specifics are configurable through the controller in order to facilitate communication with other devices as is required. In asynchronous operation, devices use start and stop bits to signal to each other when to talk and when to listen, and never speak at the same time.

UART Buffer

In a Universal Asynchronous Receiver / Transmitter, a buffer is used to store a small volume of data before it is processed. This means that both devices have a slight delay in processing each other's data, but allows a safe interval to prevent lost data in case of interference or bad packets. In addition, it gives each device lead time to process an interrupt command from the other device. The UART buffer is somewhat analogous to a tape delay in live television broadcasts.


User Datagram Protocol. A communications protocol like TCP. Unlike TCP, UDP sends messages as a whole and not as packets. UDP also does not ensure all of a message has been sent and has arrived in the correct order. Widely used for streaming audio or video.

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UNII Bands

In the United States and other countries that adhere to FCC policy, the 5 GHz band is divided into the following four sub-bands referred to as Unlicensed National Information Infrastructure (UNII) bands:

  • UNII-1: 36, 40, 44, 48
  • UNII-2: 52, 56, 60, 64
  • Intermediate: 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140
  • UNII-3: 149, 154, 159, 165

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Unipole Antenna

A type of antenna very similar to the monopole. It consists of a single conducting rod mounted to a conductive surface. The unipole also has a series of wires attached to the top of the rod and the base. This design is meant to alleviate issues with AM broadcast antenna installations.

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