CentreCOM
AT-3624TS/AT-3624TRS Repeaters
51
PHYSICAL SIGNALING (PLS)—That portion of the physical layer
contained within the DTE that provides the logical and functional coupling
between MAU and data link layers.
POLARITY CORRECTION—Many 10BASE-T UTP ports have a polarity
correction function. If the UTP wiring has RD- and RD+ inadvertently crossed,
the polarity correction function will sample the signal and electrically swap the
wires. If the TD- and TD+ wires are crossed, the correction would occur at the
MAU on the other end of the UTP link. This occurs within a single pair and
should not be confused with the crossovercrossover cable.
PROPAGATION DELAY—The time it takes a signal to travel from the input
of a system component to the output. Usually measured in nanoseconds. IEEE
802.3 has specific propagation delay maximums for computing propagation
budgets when designing a LAN. Cable length plays a major role in propagation
delay. [i.e, a 50 meters (164 ft.) AUI cable has a maximum allowable
propagation delay of 257 ns.] The propagation delay of cable is dependent on
length and velocity factor of the cable type. There are also propagation delays
associated with electronics attached to the system.
PUNCH-DOWN BLOCK—The punch-down block is the wiring panel where
the house wiring from the building’s offices terminates. This is where many
10BASE-T hubs would be located. Wiring installers use a special punch-down
tool to insert the UTP wire for data and voice applications.
REPEATER—A device used to extend the length, topology, or
interconnectivity of the physical medium beyond that imposed by a single
segment, up to the maximum allowable end-to-end trunk transmission line
length. Repeaters perform the basic actions of restoring signal amplitude,
waveform and timing applied to normal data and collision signals.
RJ45—This connector is a 10BASE-T standard for connecting UTP cabling.
They are inexpensive and easy to install onto UTP cable.
SIGNAL QUALITY ERROR (SQE)—Also referred to as Collision or Collision
Presence. This occurs when two devices attempt to transmit at the same time
which is an illegal condition.
SIMPLE NETWORK MANAGEMENT PROTOCOL (SNMP)— SNMP is a
TCP/IP protocol that generally uses the User Datagram Protocol (UDP) to
exchange messages between a management information base and a
management client residing on a network. Since SNMP does not rely on the
underlying communication protocols, it can be made available over other
protocols, such as XNS or DECnet.
SLAVE— A repeater that behaves as a “dumb” module managed by a Master
in a department concentrator chassis. Slaves operating standalone perform
only simple regeneration and retiming tasks associated with repeating and are
not manageable.
SQE TEST—Commonly referred to as Heartbeat, is a special 802.3 signal sent
by the MAU to the DTE to test the collision detection function. Some DTE want
SQE and others do not. Repeaters do not want SQE Test.
STANDADLONE—Repeater operating as a hub on its own; i.e., not a module
among other modules in a department concentrator chassis.
