Specifications

Page C–4
FOCUS System Manual
generates timing signals for the control of other
clocks in the system.
Megabyte Specifically one million bytes,
commonly used to indicate 1,048,576 bytes.
Minor Alarm A designation for an alarm indi-
cating a failure that affects one a channel or one or
more other less critical abnormal conditions.
Module PC board.
u-law The PCM coding and companding standard
used in Japan and North America.
Multiplex (MUX) To interleave, or transmit two
or more messages on a single channel.
Multiplexing The process of dividing a transmis-
sion facility into two or more channels.
M13 A designation for a multiplexer which
connects 28 DSls to one DS3 circuit.
Near-end Cross Talk Crosstalk that is propagated
in a disturbed channel in the direction opposite to
the direction of propagation in the disturbing
channel.
Network The configuration of two or more
terminals with interconnecting T1/E1 links.
Octet Agroup or byte that consists of eight binary
digits and is usually operated upon a single entity.
Orderwire Voice channel that can be used
between terminals.
NRZI Non Return to Zero Inverted. A binary
encoding scheme that inverts the signal on a “one”
and leaves the signal unchanged for a “zero”.
PBX (Private Branch Exchange) A private
telephone exchange connected to the public
telephone network on the user’s premises.
PCM (Pulse Code Modulation) A voice digitiza-
tion technique programmed for 64 Kbps (8 bits
per sample times 8 Kbps) per voice channel.
PDH Plesiochronous Digital Hierarchy.
Developed to carry digitized voice over twisted
pair cabling more efficiently.
PLOW An acronym for Party Line OrderWire.
Voice channel that can be used by all terminals in
a system.
Primary Path The initial route that is established
as the communication path. It is the same origin
and destination, but a different path than the
alternate.
Protocol The rules for communication system
operation that must be followed if communication
is to be effected.
Pulse Length The time interval between the rising
edge and the falling edge of a pulse.
Reconfiguration The act of changing Time slot
assignments either manually or automatically.
Redundant Power Supply A spare power supply
used as backup for another power supply.
Refraction The bending of rays as they pass from
one medium to another.
Reframing Time The time it takes to resync after
sync is lost and then returns.
Ringdown The method of signaling another
terminal in which the remote telephone rings
when the local telephone is raised off the hook.
RS-232 An EIA specified physical interface, with
associated electrical signaling, between data
communications equipment (DCE) and data
terminal equipment (DTE).
RS-422 An EIA specification defining the elec-
trical characteristics of balanced voltage digital
interface circuits.
RS-530 An EIA specification defining the elec-
trical characteristics of unbalanced voltage digital
interface circuits.
RTU Remote Terminal Unit.
Sample The value of a particular characteristic of
a signal at a chosen instant.
Sampling The process of taking samples, usually
at equal time intervals.
Sampling Rate The number of samples per unit
time (e.g., rate of sampling a voice signal).
SDH Synchronous Digital Hierarchy. SDH is a
CCITT defined standard technically consistent
with SONET (i.e., another name for SONET).
Self-Testing Acircuit that can perform tests on