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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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17: <script type="text/javascript" language="javascript" src="scripts/misc.txt"></script>
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20: <h4>table of Contents</h4>
21: <ul>
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"x3"x2" 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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