![](http://datasheet.mmic.net.cn/Silicon-Laboratories-Inc/SI2494-A-GM_datasheet_102086/SI2494-A-GM_38.png)
Si2494/39
38
Rev. 1.0
+VLS = n
Analog Source / Destination Select.
n
Description
0
ISOmodem on-hook. AOUT disabled. Tone detectors disabled. Si3000
sample pass-through to DAA is inactive.
1
ISOmodem off-hook. AOUT disabled. Tone detectors disabled.
4
ISOmodem on-hook. AOUT connected to ISOmodem tone generators. Tone
detectors disabled.
5
ISOmodem off-hook. AOUT connected to PSTN. Tone detectors enabled.
15
ISOmodem goes off-hook, begins V.253 tone event reporting and Si3000 to
DAA sample pass-through becomes active. Dial tone can be heard on handset.
20
ISOmodem on-hook. AOUT disabled. Tone detectors enabled.
21
ISOmodem on-hook. AOUT connected to ISOmodem tone generators. Tone
detectors enabled.
+VNH = <hook>
Automatic Hangup Control.
<hook>
Hook control description
0
The ISOmodem retains automatic hangups as is normal in the other
modes (such as hanging up the phone when the ISOmodem does not
detect a data carrier with a given time interval).
1
The ISOmodem shall disable automatic hangups in the other non-voice
modes.
2
The ISOmodem shall disable all hang-ups in other non-voice modes. The
ISOmodem shall only perform a “l(fā)ogical” hangup (return the OK result
code).
+VRA = n
Ringing Tone Goes Away Timer.
The ISOmodem only uses this command in call origination transactions. This command sets
the amount of time in 0.1 second units the ISOmodem shall wait between Ringing Tone
before it can assume that the remote modem has gone off-hook. Default time is five sec-
onds.
+VRID = n
Repeat Caller ID.
n
Description
0
Display Caller ID information of the last incoming call in formatted form.
1
Display Caller ID information of the last incoming call in unformatted form.
+VRN = n
Ringing Tone Never Appeared Timer.
This command sets the amount of time in seconds the ISOmodem will wait looking for Ring-
ing Tone. If the ISOmodem does not detect Ringing Tone in this time period, the ISOmodem
shall assume that the remote station has gone off-hook and return an OK result code.
Default time is 0 seconds.
Table 10. Basic AT Command Set (Command Defaults in Bold) (Continued)
Command
Action