Black Box 32144, Руководство пользователя

Страница: 140 / 195

48
MODEM 32144
AUTO. This selection configures
the modem for V.32/208 auto-detect
mode. This mode allows the modem
to automatically select V.32 or Bell
208 operation, depending on the
mode of the originating modem.
Note—
• To enable V.32/208 auto-detect
mode, the Speed Type option
must be set to AUTO and the
V.32/208 auto-detect Summary
Setup option must be set to 1
for enable. This option is
shown in
Appendix B, Fig. B-6 .
• Selecting the V.32/208 Quick
Setup automatically sets the
speed type to AUTO—and
enables the Summary Setup
auto-detect option (sets it to 1).
• When the speed type is set to
AUTO, the ALX will not
handshake in V.22 bis, Bell
212/103 or V.21/V.22,V.23
mode.
• All information in the 208
section above applies to
V.32/208 auto-detect mode.
Three options intended only for
208A/B and V.33 operation are
accessible through MODEM
SETUPS screen 7. These options
allow you to select constant or
switched carrier, set CTS to follow
RTS or set CTS to be always on,
or specify an RTS-CTS delay time.
For further information, see the
Carrier, CTS, and RTS-CTS Delay
headings later in this chapter.
For further information on Bell
208 mode, see chapter (section
titled Dumb Mode and Bell 208
Operation).
3.6 V.42 Error Correction Options
The modem supports both
CCITT V.42 error correction and
Microcom Networking Protocol
(MNP) error correction (classes 1
through 5). V.42 and MNP both
provide end-to-end error
correction through an automatic
repeat-transmission request
algorithm. Both types of error
correction enable the modem to
detect data-transmission errors
and automatically request
retransmission of adversely affected
data until it is received correctly.
Either error-correction standard
(V.42 or MNP) may be enabled for
either dial or leased-line operation.
However, error correction can
function only if all of the following
conditions are present:
• The modem that the modem
is communicating with must be
equipped with the same type of
error correction (V.42/V.42 bis
or MNP).
• The same type of error
correction (V.42/V.42 bis or
MNP) must be enabled at both
ends of the communication
link.
• Both communicating modems
must be configured for
asynchronous data format.