external/bsd/ntp/dist/html/gadget.html

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   7                 <title>Gadget Box PPS Level Converter and CHU Modem</title>
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  12                 <h3>Gadget Box PPS Level Converter and CHU Modem</h3>
  13                 <img src="pic/gadget.jpg" alt="gif" align="left">A Gadget Box built by Chuck Hanavin
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  15                 <h4>Related Links</h4>
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  20                 <h4>table of Contents</h4>
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  22                         <li class="inline"><a href="#intro">Introduction</a></li>
  23                         <li class="inline"><a href="#ckt">Circuit Description</a></li>
  24                         <li class="inline"><a href="#file">Files</a></li>
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  27                 <h4 id="intro">Introduction</h4>
  28                 <p>Many radio clocks used as a primary reference source for NTP servers produce
  29                         a pulse-per-second (PPS) signal that can be used to improve accuracy to a
  30                         high degree. However, the signals produced are usually incompatible with the
  31                         modem interface signals on the serial ports used to connect the signal to
  32                         the host. The gadget box consists of a handful of electronic components assembled
  33                         in a small aluminum box. It includes level converters and a optional radio
  34                         modem designed to decode the radio timecode signals transmitted by the Canadian
  35                         time and frequency station CHU. A complete set of schematics, PCB artwork,
  36                         drill templates can be obtained via the web from ftp.udel.edu as <a href="ftp://ftp.udel.edu/pub/ntp/hardware/gadget.tar.Z">gadget.tar.Z</a>.</p>
  37                 <p>The gadget box is assembled in a 5&quot;x3&quot;x2&quot; aluminum minibox containing the level converter and modem circuitry. It includes two subcircuits. One of these converts a TTL positive edge into a fixed-width pulse at EIA levels and is for use with a timecode receiver or oscillator including a TTL PPS output. The other converts the timecode modulation broadcast by Canadian time/frequency standard station CHU into a 300-bps serial character stream at EIA levels and is for use with the <a href="drivers/driver7.html">Radio CHU Audio Demodulator/Decoder</a> driver.</p>
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