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Excessive Bipolar
Violation Condition
Extended Superframe
Format (ESF)
Facsimile
Failed Second (FS)
Failed Signal State
511-Bit Test Pattern
Frame
Frame
Synchronization
Bit Error Event
Fusible Link
Ground
Handshake Protocol
Interface
Jitter
Keep Alive Signal
GLOSSARY
An excessive bipolar violation condition occurs when more than 1,544 bipolar vio-
lations (BPVs) occur in 1,000 consecutive seconds. The condition clears when no
BPVs occur for 85 consecutive seconds. A BPV is the occurrence of two or more
consecutive bits in the DS1 signal that do not alternate between signal levels as
required by the network for the Alternate Mark Inversion (AMI) line code.
ESF is an extension of the D4 framing format, combining 24 frames of 193 bits
each into an extended superframe, and providing improved performance
ing capabilities and protection against false framing.
The communications process in which graphics or text documents are scanned,
transmitted via a (typically dial-up) phone line, and reconstructed by a receiver;
facsimile device operation typically follows one of the CCITT standards for in-
formation representation and transmission (Group 1 analog, with page transmis-
sion in four or six minutes; Group 2, with page transmission in two or three min-
utes, and Group 3 digital, with page transmission in less than one minute); also
Fax.
An FS is counted for every second a failed signal state exists.
A failed signal state occurs when 10 consecutive severely ESs occur. A failed sig-
nal state ends when 10 consecutive seconds of data are processed and no severely
ESs occur. While in a failed signal state, no ESs are counted. For every second a
failed signal state exists, an FS results.
An irregular, quasi-random pattern of 511 bits used to test and measure network
jitter.
A group of bits sent serially over a communications channel; generally a logical
transmission unit sent between data-link-layer entities that contains its own con-
trol information for addressing and error checking; the basic data transmission
unit employed with bit-oriented protocols similar to blocks.
This is the occurrence of a bit error within the framing-pattern-sequence of an
ESF superframe.
Thin printed circuit fuses on pc boards that open if ground potential exceeds 0.25 V
rms between pc board and peripheral equipment.
An electrical connection or common conductor that, at some point, connects to the
earth.
In communications, a predefined exchange of signals or control characters be-
tween two devices or nodes that sets up the conditions for data transfer or trans-
mission; also, handshaking.
A shared boundary; a physical point of demarcation between two devices, where
the electrical signals, connectors, timing, and handshaking are defined; the pro-
cedure, codes, and protocols that enable two entities to interact for the meaningful
exchange of information.
The slight movement of a transmission signal in time or phase that can intro-
duce errors and loss of synchronization for high-speed synchronous communica-
tions; see Phase Jitter.
A keep alive signal prevents the network's line regenerators from oscillating
(which causes interference with adjacent channels). The network requires that
B-5
monitor-
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