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Chapter 4 – V.8 / V.8bis Commands
Multi-Tech Systems, Inc. AT Commands Reference Guide (S000273F) 40
Chapter 4 – V.8 / V.8bis Commands
V.8 is a way V.34 modems negotiate connections features and options, and V.8bis is a start-up sequence for
multimedia modems.
Command: +A8E V.8 and V.8bis Operation Controls
Description: This command is defined for two conditions: as a parameter while the modem is on-hook,
and as an action command while the modem is off-hook. If enabled, V.8 negotiation does
not preclude simultaneous implementation of other negotiation means (e.g., V.8bis, V.18,
V.32bis Annex A). It is a compound parameter if issued while the modem is on-hook, used
to precondition V.8 and V.8bis originating and answering operation. It is issued by the
DTE before the Dial (D) or Answer (A) command, regardless of the state of the +FCLASS
parameter. This command is an action command if issued while the modem is off-hook to
(re)start V.8 or V.8bis negotiation.
Example: If initial V.8 negotiation fails, but subsequent T.30 negotiation indicates V.8
capability, this command may be used to initiate V.8 negotiation.
Syntax: +A8E=<v8o>,<v8a>,<v8cf>[,<v8b>][,<cfrange>][,<protrange>]
Values: <v8o> Decimal number which enables/disables issuance of +A8x indications
during modem-controlled V.8 origination negotiation.
1 Enable DCE-controlled V.8 origination negotiation without +A8x
indications. Default
6 Enable DCE-controlled V.8 origination negotiation with +A8x
indications.
<v8a>= Decimal number which enables/disables issuance of +A8x indications
during modem-controlled V.8 answer negotiation.
1 Enable DCE-controlled V.8 answer negotiation without +A8x
indications. Default
5 Enable DCE-controlled V.8 answer negotiation with +A8x
indications.
<v8cf>= Set the V.8 CI signal call function to the hexadecimal octet XY
00 Default
21
C1
<v8b>= Decimal number which enables/disables V.8bis negotiation.
0 Disable V.8bis negotiation.
1 Enable V.8bis negotiation. Default
<cfrange>= “<string of values>“. Applicable only for <v8a>=5. Not supported.
< protrange >= <string of values>“. Applicable only for <v8a>=5. Not supported.
Default Values: 1,1,00,1,0,0
The ATD and ATA commands behave as specified in V.250, and +A8n indications are not
generated by the modem. For subparameter values <v8o>=6 and <v8a>=5, +A8I
indications are issued during the V.8session to notify the DTE when the relevant V.8
signals are received.
Report Commands: +A8E? Reports current or selected values.
+A8E=? Reports supported range of parameter values.
Command: +A8I CI Signal Indication
Description: This indication is issued by an answering modem, if +A8E,<v8a> .0, to indicate detection
of a V.8 CI signal and report the recovered Call Function octet(s).
Indication Syntax: +A8I:<v8cf><CR>
Values: <v8cf> A hexadecimal code octet representation of those Call Function octet(s).
+A8I:0 indicates that the modem timed out waiting for CI.
Example: +A8I:0 The modem timed out waiting for CI.
+A8I:X YYY