IBM 300 Service Manual page 149

and coding between a data terminal equipment (DTE)
and a line. A DCE can be separate piece of equipment
or part of other equipment.
data terminal equipment (DTE). That part of a data
station that serves as data source, data sink, or both,
and provides the data communication control function
depending on the type of protocol used.
dB. Decibel.
dBm. Decibel based on 1 milliwatt.
DC48. Dc power input type -48V
dc. Direct current.
DCD. Dc distribution (module).
DCE. Data circuit-terminating equipment.
DDI. Direct dialing-in.
DE. Discard eligibility.
decibel (dB). (1) One tenth of a bel. (2) A unit that
expresses the ratio of two power levels on a logarithmic
scale. (3) A unit for measuring relative power. The
number of decibels is 10 times the logarithm (base 10)
of the ratio of the measured power levels; if the
measured levels are voltages (across the same or equal
resistance), the number of decibels is 20 times the log
of the ratio.
decibel based on 1 milliwatt (dBm). A unit of
absolute power measurement that is scaled such that 0
dBm equals 1 milliwatt.
dialog box. On the screen of a station, an area with
entry fields and push buttons. (Also called dialog.)
DLCI. Data link connection identifier.
DNPT. Destination numbering plan table.
DSP. Digital service processor.
DSU. Data service unit.
DTE. Data terminal equipment.
DTMF. Dual-tone modulation frequency.
DTR. Data terminal ready.
dummy module. In an Nways Switch, a cover inserted
in the place of a module to ensure correct air cooling
inside a logic subrack. During normal operation, the
dummy modules must not be removed.
E1 standard. A European standard for TDM digital
transmission service at 2.048 Mbps.
E3 standard. A European standard for TDM digital
transmission service at 34.368 Mbps. An E3 line can
transport up to 16 E1 circuits.
E&M. Earth & mark.
ECMA. European Computers Manufacturers
Association.
EIA. Electronics Industries Association.
equivalent capacity. The minimum amount of
bandwidth needed by a connection to ensure that the
packet loss ratio is below a specified threshold.
ESF. Extended status flags.
ETS. European telecommunication standard.
FANB. Fan box.
FAT. File allocation table.
fax. Document received from a facsimile machine.
Synonym for telecopy.
FCS. Frame check sequence.
FDDI. Fiber Distributed Data Interface.
FE1. Fractional E1.
FECN. Forward explicit congestion notification.
FEP. Front-end processor.
fiber. Synonym for optical fiber.
fiber budget. The optical power loss as result of the
number of connections in the optical fiber link
subtracted from the working budget. The loss as a
result of connections includes connector loss and splice
loss. The fiber budget is expressed in decibels.
Fiber Distributed Data Interface (FDDI). A U.S.
standard for 100 Mbps token-ring LANs using optical
fiber cables over distances of several kilometers.
fiber optic cable. Synonym for optical fiber.
FR. Frame relay.
FRAD. Frame-relay access device.
frame relay (FR). A connection-oriented protocol to
transport data frames over a fast packet-network with
guaranteed end-to-end quality of service.
FRFH. Frame-relay frame handler.
front-end processor (FEP). A processor, such as the
IBM 3745, 3746 Model 900 or 950, or 3174, that
relieves a main frame from communication control
tasks.
E-3
Glossary