NonStop S-Series Server Description Manual (G06.24+)

Glossary
HP NonStop S-Series Server Description Manual—520331-003
Glossary-28
electromagnetic interference (EMI)
electromagnetic interference (EMI). Forms of conducted or radiated interference that
might appear in a facility as either normal or common-mode signals. The frequency of
the interference can range from the kilohertz to gigahertz range. However, the most
troublesome interference signals are usually found in the kilohertz to low megahertz
range. At present, the terms electromagnetic interference and radio frequency
interference (RFI) are usually used interchangeably.
electrostatically shielded transformer. A transformer that has a metallic shield placed
between the primary and secondary windings. This shield diverts high-frequency
signals to ground.
electrostatic discharge (ESD) protection kit. A kit containing an antistatic mat and a
wriststrap with a cable and grounding clip. A service provider or customer wears the
wriststrap while performing maintenance procedures inside an enclosure. The
wriststrap and cable contain grounding wires so that when the grounding clip is
attached to a metal object, such as the enclosure, the person wearing the wriststrap is
grounded and any static electricity incurred during the procedure is discharged safely
to the enclosure instead of to electrical components within the enclosure.
ELF. See extended link format (ELF).
emergency power off (EPO). Describes equipment used to automatically disconnect all
electrical power to connected equipment if there is an emergency. A computer room’s
main EPO system shuts off all room equipment (except for lighting and fire-sensor
equipment) if there is a fire. An equipment zone EPO shuts off power to all connected
computer equipment if a power anomaly occurs.
emergency power-off (EPO) connector. A two-pin connector on the service side of an
enclosure that allows an external signal to disable the batteries in the enclosure during
emergency conditions. A cable is attached from the connector to a relay band or push
button typically located near the door of a computer room. Pushing the EPO button
removes power from all computer equipment in the room. The EPO connectors prevent
the batteries from powering the server after power is removed. EPO capabilities are
required in the United States when a server is installed in a computer room designed to
comply with the special construction and fire protection provisions of the United States’
national electrical code (or at other sites as required by local regulations.)
EMI. See electromagnetic interference (EMI).
emitter-coupled logic (ECL). A logic that expresses digital signals in differential negative
voltage levels, from -8 volts to -1.8 volts. HP NonStop™ S-series servers containing
ServerNet expansion boards (SEBs) use ECL ServerNet cables. An ECL plug-in card
(PIC) allows the modular SEB (MSEB) and I/O multifunction (IOMF) 2
customer-replaceable unit (CRU) to use ECL ServerNet cables.
emitter-coupled logic (ECL) plug-in card (PIC). A plug-in card (PIC) for the modular
ServerNet expansion board (MSEB) and I/O multifunction (IOMF) 2 customer-