VOCP System - Install

VOCP System - Install - Modems

VOCP requires a functional voice modem to perform it's call answering function - one that is supported by vgetty. If you are having difficulty with your modem this page can help you out.

This document describes basic interaction and queries to your voice modem. It is aimed primarily at helping you troubleshoot your modem, in cases where you've been through the vgetty installation and the mgetty/vgetty docs and still can't get some (or all) features of your modem working.

   - Installing the modem
   - Interacting with the modem
      - starting minicom
      - querying the modem
      - quitting minicom
   - Conclusion

Installing the modem

We will not attempt to describe everything you need to know in order to install and configure your modem - please see the Modem-HOWTO or one of the other related HOWTOs from the linux documentation project

Which modem should you install? Vgetty and VOCP are evolving and the list of supported modems changes - as does the modems that are available at your local outlets. A somewhat outdated list may be found on the vgetty modem database page. Modems that have been reported to function are

Zyxel 1496 and 2864
MultiTech MultiModem MT2834 ZDX V and MT5600ZDXV External
ELSA MicroLink TQV series
US Robotics/3Com 56K Voice FaxModem Model 5610
Diamond 56e Pro voice
External Zoom/Faxmodem V.92
Zoom 56K PCI internal
Many others...

If you have a real voice modem and it's from one of these brands, chances are you can get it working. Even if your modem is not in the list, you still have hope - the latest vgetty may recognize it automatically or you may be able to use the force_detect patch (see the vgetty installation page).

If you are unsure about your modem model or its capabilities, the text below will help you out.

Interacting with the modem

The most direct way to figure out your modem's capabilities are:

read the modem's manual
ask the modem

If you have access to the modem's manual from your manufacturer, you may be in luck. If it is more than mere marketroid fluff and includes information about the chipset and AT command set used, you should have everything you need. Read it, focusing on voice and/or caller id related info.

If you can't find the modem docs, didn't like the modem related HOWTOs at http://www.tldp.org/ or just like getting hands on experience, it's time to whip out minicom.

starting minicom
If you are new to minicom, here is a little guide that should get you started.

Open a console or xterm. As root, start minicom, with the setup switch
# minicom -s
In the configuration menu that appears, use the arrow keys to go down to serial port setup, hit <ENTER>.

You can see the first line in the new screen is something like:
A -    Serial Device      : /dev/modem
Hit the 'A' key to edit this field and erase the /dev/modem. If you know which tty your modem is on, enter it now. If you do not, start by trying /dev/ttyS0 and work your way up (ttyS1, ttyS2...).

Hit the <ENTER> key to complete the edit and <ENTER> to exit this menu. Use the arrow keys to go down to Exit (not Exit from Minicom!), press <ENTER>.

You will see an "Initializing Modem" screen. Then, if all goes well, you will see something like:
AT S7=45 S0=0 L1 V1 X4 &c1; E1 Q0                                                
OK
Great, you are now online with your modem. If you see nothing at all, get an error message or nothing happens when you type "AT<ENTER>", try again using the next ttyS[123].

modem queries
The AT (often called "Hayes") command set used by your modem may and will probably differ from that shown here. Often times, if you don't have the manual handy and can't find anything relevant on the net, you can guess at variations, for instance replacing '+' characters with '#' and vice versa.

Ask your modem a few basic questions and ponder the responses. Some commands will ouput interesting info, all should ouput some kind of status (OK/VCON/CONNECT/other stuff when things are going well, ERROR otherwise). Here are a few information queries that may produce interesting results:
ATI
ATI3
ATI9
ATI11
AT&Vn;
Now that you've gotten to know your modem a bit better, try a few commands to determine it's capabilities and settings.
AT+FCLASS=?
or
AT#CLS=?
Will show the "modes" in which the modem may be set, often these are :
0   - data
1   - fax 1
2   - fax 2
2.0 - fax 2.0
8   - voice
You can query the current mode using:
AT+FCLASS?
And set it, for instance to voice mode, using
AT+FCLASS=8
Certain commands will only function from within a specific mode, so if your trying out voice related commands be sure to do an
AT+FCLASS=8
before proceeding. If you get an ERROR or the only modes supported are 0,1,2 you may not have a voice modem, but check the docs to make sure. Now we can try to see the available voice compression modes. These will vary between modems. Use
AT+VSM=?
AT#VCI=?
Here's the output for a Hayes accura v.92 external (Lucent Venus chipset):
AT+VSM=?
128,"8-BIT LINEAR",(7200,8000,11025)
129,"16-BIT LINEAR",(7200,8000,11025)
130,"8-BIT ALAW",(8000)
131,"8-BIT ULAW",(8000)
132,"IMA ADPCM",(7200,8000,11025)
OK
And here's the output for an old GVC (cirrus logic CL-MD56xx chipset):
AT+VSM=?
0,"8-Bit Linear",8,0,(4800,7200,8000,9600,11025),(0),(0)
1,"16-Bit Linear",16,0,(4800,7200,8000,9600,11025),(0),(0)
2,"4-Bit ADPCM",4,0,(4800,7200,8000,9600,11025),(0),(0)
128,"8-Bit Linear",8,0,(4800,7200,8000,9600,11025),(0),(0)
129,"16-Bit Linear",16,0,(4800,7200,8000,9600,11025),(0),(0)
132,"4-Bit ADPCM",4,0,(4800,7200,8000,9600,11025),(0),(0)
140,"CL1",8,0,(4800,7200,8000,9600,11025),(0),(0)
141,"3-Bit ADPCM",3,0,(4800,7200,8000,9600,11025),(0),(0)
The possibilities are quite different on the two modems and so are the default settings for voice compression:
Hayes:
 at+vsm?
 129,"16-BIT LINEAR",8000
GVC:
 at+vsm?
 140,8000,0,0
You should try out some other voice parameter queries, using either the "list all" (i.e. =?) or "show current" (i.e. ?) suffix:
AT+VLS or AT#VLS (Analog source/destination selection and DTMF/tone reporting) - try AT+VLS=? and AT#VLS=?
AT+VCID or AT#CID (caller id enable) - Try AT+VCID=? or AT#CID=?

The actual AT commands to use are, as stated above, completely modem dependent and vary (wide|wild)ly but with standards like IS 101 things seem to be getting a little better. Here are a few voice related AT commands that you can try out.

AT+VIP Initialize voice parameters.

AT+VCID Caller-ID.

AT+VDR Distinctive ring.

AT+VGT Speaker volume control.

AT+VIT DTE/DCE inactivity timer.

AT+VNH Automatic hang-up control.

AT+VLS Analog source/destination selection and DTMF/tone reporting.

AT+VTD Set beep tone duration timer.

AT+VSD Set silence detection timer.

AT+VRA Set ringback goes away timer.

AT+VRN Set ringback never came timer.

AT+VTS DTMF/tone generation.

AT+VTR Start full-duplex voice transmission and reception process.

AT+VTX Enter voice transmit state.

AT+VRX Enter voice receive state.

AT+VSM Voice compression method.

AT+VEM Event reporting and masking.

AT+VGR Receive gain selection.

AT+VPR Select DTE/DCE interface rate.

AT+VGM Microphone gain.

AT+VGS Speaker gain.

quitting minicom
When you are done, you should exit minicom cleanly such that it resets your modem to a nice state. To do so, hit:
^A 
(Ctrl-A) then
X
Say yes and begone. If you are currently running vgetty, you've probably disrupted it's operation by buggering about with the modem like this so the best thing is to restart vgetty:
# killall vgetty

Conclusion

You should now have a clearer understanding of both your modem's operation and it's capabilities. Note that even if you managed to elicit some sane responses for caller-id related commands, it doesn't mean your modem actually supports it - only that its chipset does (see the Caller ID section).

On the other hand, if you managed to get your modem into voice mode (FCLASS/CLS 8), there is a good chance that you can have fun with voice and VOCP operation.

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