heartbeat
1. <networking> The signal emitted by a Level 2 Ethernet transceiver at
the end of every packet to show that the collision-detection circuit is still
connected.
2. A periodic synchronisation signal used by software or hardware, such as a bus
clock or a periodic interrupt.
3. The "natural" oscillation frequency of a computer's clock crystal, before
frequency division down to the machine's clock rate.
4. A signal emitted at regular intervals by software to demonstrate that it is
still alive. Sometimes hardware is designed to reboot the machine if it stops
hearing a heartbeat. See also breath-of-life packet, watchdog.
[Jargon File]
(1996-03-12)
Nearby terms:
heads down « head-strict « heap « heartbeat »
heatseeker » heat sink » heat slug
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