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V.120
The remaining Mode values (whose names start with BV for B-channel V.120
protocol) are appropriate selections for circuit switched connections to
equipment supporting this new industry standard rate adaption protocol. Two
different ''frame'' modes are supported: Unnumbered Information frame (UI-
frame) mode, and (Numbered) Information frame (I-frame) mode. UI-frame
mode is more efficient than I-frame, but is not error corrected, while I-frame
mode is less efficient than UI-frame, but is error corrected. I-frame mode is
packet-oriented and uses the PAD data options.
Two different channel bandwidths are supported: 64 kbps and 56 kbps.
Select BV64U for uncorrected (UI-frame) mode connections over
64 kbps facilities.
Select BV64I for error corrected (I-frame) mode connections over
64 kbps facilities.
Select BV56U for uncorrected (UI-frame) mode connections over
56 kbps facilities.
Select BV56I for error corrected (I-frame) mode connections over
56 kbps facilities.
Note:
Parity
Option Values: odd, even, mark, space
Applicable Data Protocols: All
The ADM ignores parity received from your terminal in Local Mode. If a terminal connected
to the ADM requires parity to display Local Mode text, match the parity of the ADM with
your terminal.
Note:
The Parity setting of the ADM only affects local mode. The ADM never adjusts parity
of data transmitted to the network in data mode. The ADM only adjusts the parity of
X.25 data transmitted from the network if it is specifically requested to do so via an
X.29 message from a remote X.25 host.
During a circuit switched data call, your ADM transports all eight bits of an
asynchronous data character end-to-end as information, rather than checking or
generating a parity bit. V.120 data calls are accepted by your ADM from endpoints
provided the parity setting carried within the call setup information indicates a valid
character size and parity combination: 8-bit none, 7-bit odd, 7-bit even, 7-bit mark, or
7-bit space. V.120 data calls initiated from your ADM contain parity setting
information in the call setup information which is fixed at 8-bit no parity regardless of
the local mode parity setting. In other words, no matter what the setting of the parity
option (odd, even, mark, or space), your ADM always originates V.120 data calls with
call setup information coded as 8-bit no parity. If the called V.120 endpoint requires an
4-12
Data Options and Profiles
For further information about the new industry standard V.120 rate
adaption protocol, you can obtain ANSI Standard T1.612 from the
American National Standards Institute, 1430 Broadway, New York,
NY 10018.
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