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Document ID: CFLR-3NBEH6 |
7855 Modem - Can a 7855 modem communicate with V.32 bis modems at 7200 bps or 12000 bps?
Applicable to: World-Wide
Question:
Can a 7855 modem communicate with V.32 bis modems at 7200 bps or 12000 bps?
Answer:
It depends on the exact implementation of V.32 bis in the non-IBM modem. We have found some V.32 bis modems that inter-work just fine with the 7855 and others that will not do 7200 or 12000 bps with the 7855. The thing to do is to ask the modem vendor EXACTLY how their modem interprets the case of rate sequence bit 4=0 and bit 9=1. The desired answer is that the non-IBM modem will connect at 7200 bps and will not do the V.32 bis speed change technique.
Here are some details:
V.32 and V.32 bis modems negotiate the connection speed and some features by exchanging bit patterns called "rate sequences" during the handshaking at the beginning of a connection. For the most part, V.32 and V.32 bis rate sequences are identical. For example, B6=1 means "I support 9600 bps". For another example, in V.32 bis, B9=0 means "I do not support 7200 bps" and in V.32 B9 is required to be 0 at all times (since V.32 does not support 7200 bps). Thus B9=0 means "no 7200 bps" for both a V.32 and V.32bis modem. It is not so clear what B9=1 means for a V.32 modem.
However, B4 of the rate sequence means different things in V.32 and V.32 bis as follows:
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B4=0 |
B4=1 | |
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V.32 |
V.26 ter 2400 bps not enabled |
V.26 ter 2400 bps enabled |
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V.32 bis |
interwork only per V.32 |
do V.32 bis handshake |
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Search Keywords |
v.32 7855 modem bps speeds 7200 9600 | |
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Hint Category |
Modems | |
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Date Created |
29-10-97 | |
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Last Updated |
25-11-98 | |
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Revision Date |
19-11-99 | |
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Brand |
IBM Options | |
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Product Family |
Modems | |
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Machine Type |
19.2K | |
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Model |
53F6062 | |
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TypeModel |
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