hi

i am trying to connect to a telephone using my voice modem and AT
commands. i know that the telephone modulates/demodulates data using
V.23 i.e 1200 baud FSK.

do i have to make any settings before dialing ? i am using
hyperterminal for my experimentaitons, but i intend to use VC++ for
this program

after setting my modem to work on v.23 (sending ATF3 command), i dial
the phone number (like atd 254125). it makes the phone ring and the
phone automatically receives the call, but ..... nothing happens after
wards. until i press a key and then it says NO CARRIER and hangs up.
what is the problem? the process seems simple but its not working. am i
missing something ?

please help
thanks in advance

Somia

On 4 Aug 2005 09:24:36 -0700, "Somia" <somia_iqbal@yahoo.com> wrote:

~ hi
~
~ i am trying to connect to a telephone using my voice modem and AT
~ commands. i know that the telephone modulates/demodulates data using
~ V.23 i.e 1200 baud FSK.
~
~ do i have to make any settings before dialing ? i am using
~ hyperterminal for my experimentaitons, but i intend to use VC++ for
~ this program
~
~ after setting my modem to work on v.23 (sending ATF3 command), i dial
~ the phone number (like atd 254125). it makes the phone ring and the
~ phone automatically receives the call, but ..... nothing happens after
~ wards. until i press a key and then it says NO CARRIER and hangs up.
~ what is the problem? the process seems simple but its not working. am i
~ missing something ?
~
~ please help
~ thanks in advance
~
~ Somia

Well I haven't played with V.23 very much ... I just now took a look
at it, and I see that it has zero information about training procedures.

Let me ask you this: if you call into this "telephone" from a handset,
do you hear anything?

V.23's frequencies are like this:

"mode 1" - forward channel @ 600bps
mark (1) 1300Hz
space (0) 1700Hz

"mode 2" - forward channel at 1200bps
mark (1) 1300Hz
space (8) 2100Hz

optional backward channel at 75bps
mark (1) 390Hz
space (0) 450Hz

Normally the V.23 answer modem will transmit @ 1200bps
and receive @ 75bps (and of course vice versa for the
originate modem.)

Normally an FSK modem, if using async framing, will
transmit mark frequency (i.e. async stop bits) while idle.

Therefore, we may assume that, when you call a V.23 modem,
it will transmit steady 2100Hz tone.

Or maybe this "telephone" transmits at 75bps and expects
to receive at 1200bps. In that case, I would expect that
you might hear steady 390Hz tone.

If you don't hear anything, then maybe there is a switch
or something that you need to flip on the phone to kick
it into data mode.

What do you know about this "telephone"? Does it have a
data sheet?

It's not Minitel, is it?

Hm, I just now came across V.18 which I hadn't heard about
previously:

Operational and interworking requirements for DCEs operating in the text telephone mode
http://www.access-board.gov/telecomm...ndices/v18.htm

Does this sound like the sort of thing that you're trying to do?

Aaron

what _exactly_ i am trying to do is implementing this "ETSI ES 201 912"
standard.
it is " Short Message Communication between a fixed network Short
Message Terminal equipment and a Short Message Service Centre "

http://webapp.etsi.org/exchangefolde...12v010201p.pdf


the physical layer of the protocol2 defined in this document reffers to
another standard

http://webapp.etsi.org/exchangefolde...01v010301p.pdf

"ETSI EN 300 659" which tells


"Simplex asynchronous voiceband data transmission technique is used to
transfer data to the TE. A frequency modulator is required in the LE
and a demodulator in the TE. The frequency modulator shall meet 1 200
baud V.23 [6] standard characteristics as specified in ITU-T
Recommendation V.23 [6] for the forward data transmission channel"

so its asynchornous. one start bit, 8 data bits and one stop bit. but i
dont understand why do you say that a steady tone of some frequency
should be heard ?

when i dial the telephone from some other phone, and when the telephone
is expecting the SMS (rather then an ordinary call), a small beep is
heard. which i know is the fist fsk frame that that telephone was
supposed to transmitt, which consists of 300 alternating mark and space
bits followed by 80 mark bits. after transimtting this the telephone
waits for the SMS .. and when it is not transmitted within a defined
time, it transmitts another signal (which represents error) and hangs
up.

now is there any meathod to capture these bits ? when there is no
CONNECT or CON or something...


thanks for your help

Somia

A ha - so you're trying to do SMS.

No, a garden variety landline voiceband modem that does V.23
is not going to be able to do SMS.

Methinks you'll need something like this:

http://www.landlinesms.com/

Regards,

Aaron

--


~
~ what _exactly_ i am trying to do is implementing this "ETSI ES 201 912"
~ standard.
~ it is " Short Message Communication between a fixed network Short
~ Message Terminal equipment and a Short Message Service Centre "
~
~ http://webapp.etsi.org/exchangefolde...12v010201p.pdf
~
~
~ the physical layer of the protocol2 defined in this document reffers to
~ another standard
~
~ http://webapp.etsi.org/exchangefolde...01v010301p.pdf
~
~ "ETSI EN 300 659" which tells
~
~
~ "Simplex asynchronous voiceband data transmission technique is used to
~ transfer data to the TE. A frequency modulator is required in the LE
~ and a demodulator in the TE. The frequency modulator shall meet 1 200
~ baud V.23 [6] standard characteristics as specified in ITU-T
~ Recommendation V.23 [6] for the forward data transmission channel"
~
~ so its asynchornous. one start bit, 8 data bits and one stop bit. but i
~ dont understand why do you say that a steady tone of some frequency
~ should be heard ?
~
~ when i dial the telephone from some other phone, and when the telephone
~ is expecting the SMS (rather then an ordinary call), a small beep is
~ heard. which i know is the fist fsk frame that that telephone was
~ supposed to transmitt, which consists of 300 alternating mark and space
~ bits followed by 80 mark bits. after transimtting this the telephone
~ waits for the SMS .. and when it is not transmitted within a defined
~ time, it transmitts another signal (which represents error) and hangs
~ up.
~
~ now is there any meathod to capture these bits ? when there is no
~ CONNECT or CON or something...
~
~
~ thanks for your help
~
~ Somia

please tell, why not ?
the idea in my mind was that i'll prepare the bits according to the
etsi standard and i'll give it to the modem to modulate and transmit
those bits.

and if its really not possible, are there any alternatives? coz i am
just doing a university project and buying this modem is not possible
for me.

thanks
Somia.

On 6 Aug 2005 18:11:52 -0700, "Somia" <somia_iqbal@yahoo.com> wrote:

~ >No, a garden variety landline voiceband modem that does V.23
~ >is not going to be able to do SMS.
~
~ please tell, why not ?

Because it won't be able to train. And, if it could train, it
would only be able to *send* 1200bps V.23 or *receive* 1200bps
V.23 but never both.

~ the idea in my mind was that i'll prepare the bits according to the
~ etsi standard and i'll give it to the modem to modulate and transmit
~ those bits.
~
~ and if its really not possible, are there any alternatives? coz i am
~ just doing a university project and buying this modem is not possible
~ for me.
~
~ thanks
~ Somia.


Well, I don't know what your budget is. I happen to know that the
Silicon Labs Si2493 chipset modem does support sending and receiving
SMS messages using a fake fax mode (+FCLASS=256.) It seems that others
may be able to talk SMS using +CMGR, +CMGS and friends (whether these
commands work only on a cellular modem or whether there exist landline
modems that support these commands ... I dunno; I was not able to find
any.)

Good luck.

Aaron