11 lines
2.3 KiB
HTML
11 lines
2.3 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>heartbeat</title><link rel="stylesheet" href="../../jargon.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.61.0"/><link rel="home" href="../index.html" title="The Jargon File"/><link rel="up" href="../H.html" title="H"/><link rel="previous" href="heads-down.html" title="heads down"/><link rel="next" href="heatseeker.html" title="heatseeker"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">heartbeat</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="heads-down.html">Prev</a> </td><th width="60%" align="center">H</th><td width="20%" align="right"> <a accesskey="n" href="heatseeker.html">Next</a></td></tr></table><hr/></div><dt><a id="heartbeat"/><dt xmlns="" id="heartbeat"><b>heartbeat</b>: <span xmlns="http://www.w3.org/1999/xhtml" class="grammar">n.</span></dt></dt><dd><p> 1. The signal emitted by a Level 2 Ethernet transceiver at the end
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of every packet to show that the collision-detection circuit is still
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connected. </p></dd><dd><p> 2. A periodic synchronization signal used by software or hardware,
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such as a bus clock or a periodic interrupt. </p></dd><dd><p> 3. The ‘natural’ oscillation frequency of a computer's
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clock crystal, before frequency division down to the machine's clock rate.
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</p></dd><dd><p> 4. A signal emitted at regular intervals by software to demonstrate
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that it is still alive. Sometimes hardware is designed to reboot the
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machine if it stops hearing a heartbeat. See also
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<a href="../B/breath-of-life-packet.html"><i class="glossterm">breath-of-life packet</i></a>.</p></dd><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="heads-down.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="../H.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="heatseeker.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">heads down </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> heatseeker</td></tr></table></div></body></html>
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