A
The 7858 also has an adaptive line rate
facility that automatically decreases or
increases the transmission speed to
constantly achieve the highest
performance compatible with the line
quality. It adjusts the speed if telecom-
munication line conditions degrade or
improve and according to the transmis-
sion protocol negotiated at connection
setup.
Switched Network Backup (SNBU)
capability establishes a switched
connection when a leased line is down.
A SNBU connection is associated with
a timer selected at modem setup.
With leased line monitoring one of the
following actions can occur after a time
out, depending on the modem configu-
ration:
• The active SNBU line is released and
the modem switches back to a leased
line. If the leased line is still down, a new
SNBU call is set up.
• The modem switches back to the
leased line operation without releasing
the SNBU line. If the leased line
communication is operational for one
minute, then the SNBU line is released;
otherwise the communication is
resumed through the SNBU line.
The 7858 also incorporates asynchro-
nous speed buffering, which allows the
DTE speed to remain constant even
when the modem-to-modem line speed
changes from call to call. For example,
the DTE speed might be 115.2 Kbps
while the line speed is 33.6 Kbps.
High-throughput telecommuni-
cations over switched and
leased lines
The 7858 modem operates on switched
and 2- and 4-wire leased lines. The
supported line and DTE speeds are
listed in the Supported Line and DTE
Speeds table.
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