Re: CSD calls from Neo Freerunner

[Al Johnson]

On Monday 20 January 2014 07:31:55 Michael Spacefalcon wrote:
 For those who don't know what CSD is:
 
 http://en.wikipedia.org/wiki/Circuit_Switched_Data
 
[snip test call logs] 
 
 CSD calls may be placed from a GSM mobile either to a land line or to
 another mobile.  (I don't know if it's possible to establish a CSD
 connection from a land line to a mobile.)

It's possible to establish the connection from land line to mobile, with both 
analogue and ISDN landlines. I used to use it for remote access to condition 
monitoring systems. You should be able to send and receive faxes too. It does 
need carrier support though.


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Re: CSD calls from Neo Freerunner

[joerg Reisenweber]

On Tue 21 January 2014 15:42:20 Al Johnson wrote:
 On Monday 20 January 2014 07:31:55 Michael Spacefalcon wrote:
  For those who don't know what CSD is:
  
  http://en.wikipedia.org/wiki/Circuit_Switched_Data
 
 [snip test call logs]
 
  CSD calls may be placed from a GSM mobile either to a land line or to
  another mobile.  (I don't know if it's possible to establish a CSD
  connection from a land line to a mobile.)
 
 It's possible to establish the connection from land line to mobile, with
 both analogue and ISDN landlines. I used to use it for remote access to
 condition monitoring systems. You should be able to send and receive faxes
 too. It does need carrier support though.



For landline to mobile you need to signal to carrier that the OTA connection 
shall not use GSM-codec for voice but rather establish a 9k6 data connection.
From ISDN you can set the data service class flag, from analog landline there 
is no such flag. So usually a dedicated telephone number for inbound CSD-
datacalls is mandatory and carriers rarely support this nowadays, anyway you 
have to ask your carrier to provide such number for your mobile.
IIRC there's another method where mobile switches type of a connection on the 
fly, so you'd initiate a voice call from landline to mobile and then mobile 
switches type to datacall. Can't remember what the according AT-commands been 
to accomplish that.

cheers
jOERG
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/\  www.asciiribbon.org   - against proprietary attachments
(alas the above page got scrapped due to resignation(!!), so here some 
supplementary links:)
http://www.georgedillon.com/web/html_email_is_evil.shtml  
http://www.nonhtmlmail.org/campaign.html
http://www.georgedillon.com/web/html_email_is_evil_still.shtml
http://www.gerstbach.at/2004/ascii/ (German)


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CSD calls from Neo Freerunner

[Michael Spacefalcon]

For those who don't know what CSD is:

http://en.wikipedia.org/wiki/Circuit_Switched_Data

Here is an AT command session log of me making a CSD call from my
GTA02 on T-Mobile USA:

at+cgmm
+CGMM: Neo1973 GTA02

OK
at+cgmr
+CGMR: FreeCalypso leo2moko port

OK
at+cops?
+COPS: 0,0,T-Mobile

OK
atd13034944774
CONNECT

National Institute of Standards and Technology
Telephone Time Service, Generator 1b
Enter the question mark character for HELP
D  L
 MJD  YR MO DA HH MM SS ST S UT1 msADV OTM

56677 14-01-20 05:30:54 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:30:55 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:30:56 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:30:57 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:30:58 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:30:59 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:00 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:01 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:02 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:03 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:04 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:05 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:06 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:07 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:08 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:09 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:10 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:11 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:12 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:13 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:14 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:15 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:16 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:17 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:18 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:19 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:20 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:21 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:22 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:23 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:24 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:25 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:26 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:27 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:28 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:29 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:30 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:31 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:32 00 0 -.1 045.0 UTC(NIST) *
56677 14-01-20 05:31:33 00 0 -.1 045.0 UTC(NIST) *
NO CARRIER

-- end of log --

The number I dialed in this test is the Automated Computer Time Service
provided by the National Institute of Standards and Technology:

http://www.nist.gov/pml/div688/grp40/acts.cfm

Note how the above web page says, in part: Digital modems, such as
[...] wireless modems, cannot synchronize using ACTS.  Well, the log
above clearly shows that they are wrong, at least in the case of
high-quality wireless modems like Calypso. :-)

CSD calls may be placed from a GSM mobile either to a land line or to
another mobile.  (I don't know if it's possible to establish a CSD
connection from a land line to a mobile.)  When placing a CSD call to
a land line, one can connect to a traditional dial-up modem on the
receiving end - that's how I connected to ACTS, and if you've got your
own UNIX etc server at home with an old-fashioned modem on a land
line, it is really neat to be able to connect to it from anywhere in
the world via CSD, *bypassing the Internet*!

When you place a CSD call to another mobile, the network tells the
latter that it is a CSD call rather than voice.  If you have a GTA02,
you can have some fun by testing how various other mobile phones react
to incoming CSD calls: just have your FR dial a CSD call to the number
belonging to some standard cellphone (dumb or smart), running
standard proprietary fw, and see how the latter reacts to receiving
such an unusual call. :-)  To dial a CSD call, just omit the ending
';' from the ATD command you would normally use to dial an ordinary
voice call - see my log above.

But not all modems are created equal.  I've got a Huawei E303 3G modem
in the USB stick form factor to play with, and it appears that this
modem's fw does not support CSD at all.  After doing the usb_modeswitch
voodoo typically needed for these USB 3G modems (usually automated via
udev rules, but I had to install an updated usb_modeswitch package on
my Slackware 13.37 laptop), the modem shows up as a bunch of
/dev/ttyUSBx devices, supported by the option kernel module - hence
I wonder if it's anything like the modem in the GTA04.  /dev/ttyUSB0
presents an AT command interface, and the following observations can
be made from the latter:

* One can dial voice calls with ATDnumber; - makes the phone ring on
  the other end; upon answering that call one hears noise - the modem
  must be implementing some way to pass digital audio over USB, which
  is not being