Glossary
Issue 3 June 2000
GL-7
OC-12 rings. This dual 0x1 architecture means that the VT1.5 path switching is one in the
DDM-2000 FiberReach and not in the host DDM-2000. Individual DS1 signals within an STS-1 can
therefore be dropped to DDM-2000 OC-3 shelves at several nodes around the ring. See Single 0x1.
Dual Homing
In DDM-2000 FiberReach, a network topology in which two OC-3 shelves serve as DDM-2000
FiberReach Multiplexer hosts supporting up to twelve OC-1 rings. Each DDM-2000 FiberReach
Multiplexer ring is interconnected between the two separate hosts. Two
SLC
-2000 Access Systems
serving as DDM-2000 FiberReach hosts can support up to four OC-1 rings. See Single Homing.
E
EC-1, EC-n
Electrical Carrier — The basic logical building block signal with a rate of 51.840 Mb/s for an EC-1
signal and a rate of n times 51.840 Mb/s for an EC-n signal. An EC-1 signal can be built in two ways:
A DS1 can be mapped into a VT1.5 signal and 28 VT1.5 signals multiplexed into an EC-1 (VT1.5
based EC-1), or a DS3 can be mapped directly into an EC-1 (DS3 based EC-1).
ECI
Equipment Catalog Item — The bar code number on the faceplate of each circuit pack used by
some inventory systems.
EEPROM
Electrically Erasable Programmable Read-Only Memory
EIA
Electronic Industries Association
EMC
Electromagnetic Compatibility
EMI
Electromagnetic Interference
EOOF
Excessive Out of Frame
EPROM
Erasable Programmable Read-Only Memory
EQ
Equipped (memory administrative state)
ES
Errored Seconds — A performance monitoring parameter. ES "type A" is a second with exactly one
error; ES "type B" is a second with more than one and less than the number of errors in a severely
errored second for the given signal. ES by itself means the sum of the type A and type B ESs.
ESD
Electrostatic Discharge
ESF
Extended Super Frame (format for DS1 signal)
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