Black Box 32144 Manual page 141

• The connected systems must
support data flow control
(have buffering capabilities).
Note—
• The V.42 and MNP error-
correction options (listed and
described below) are effective
only when all of the conditions
listed above are present.
• Error-correction options cannot
be changed when the modem is
on-line.
• For valid test results, disable
error correction before
running diagnostic tests.
User-selectable options let you
configure the modem for V.42
(LAPM) error correction only,
MNP error correction only, or V.42
error correction with MNP as the
fallback (alternate) error
correction protocol. Data
compression may also be enabled
by selecting either V.42 bis or MNP
class 5 error correction. Other
error-correction options are also
available.
The available error-correction
options are V.42 Mode, MNP Class
(class limit), Break Handling, V.42
Selection, Buffer Mode/Speed
Conversion, DTE Speed, DTE-DCE
and DCE-DTE Flow Control
options, and Pass-through Flow
Control. All of these options affect
the type of error correction
selected via the V42 SELECTION
screen (discussed below), except
that the MNP Class option is
CHAPTER 3: Options: Customizing the Modem Setup
applicable only to MNP operation.
The error correction options can
be selected in any order, but the
following sequence is suggested:
First select the type of error
correction desired from the V.42
SELECTION screen. Next make a
selection from the V.42 MODE
screen. Then select other error
correction options as appropriate
for your application.
Two additional error-correction
options are described near the end
of this chapter, in Section 3.16,
Options Accessible Only via
Summary Setup. These additional
options are Selective
Retransmission and DCE Pass-
through Flow Control.
V.42 Mode
Hayes, V.25 bis, Dumb, Leased-line
modes (except V.33)
The V.42 Mode settings described
below apply to the type of error
correction selected via the V42
SELECTION screen. For example,
if LAPM ONLY has been selected
as the error correction protocol,
and MANDATORY is selected from
the V42 MODE screen, V.42 or V.42
bis error correction will be
activated—or if it cannot be, the
modem will hang up.
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