CSD and Fax are seperated service?

[narke]

Hi,

Today I applied a CSD sim card from my local mobile network operator.
Actually, it seemed they don't call it CSD, but call it as fax/data
service. The strange things is that, with each of the sim card, it was
provided with three different phone number, one is voice, the other two
are fax-in/data-out and fax-out/data-in. Could anyone have some
knowledge about this? It sounds to me that fax and csd are seperated.

Thanks in advance.

[John Henderson]

Post by narke
Hi,
Today I applied a CSD sim card from my local mobile network operator.
Actually, it seemed they don't call it CSD, but call it as fax/data
service. The strange things is that, with each of the sim card, it was
provided with three different phone number, one is voice, the other two
are fax-in/data-out and fax-out/data-in. Could anyone have some
knowledge about this? It sounds to me that fax and csd are seperated.
Thanks in advance.

The OTA (over-the-air) characteristics of the three services are
different. When establishing a connection from the phone, the
phone knows which type of connection is required and will
automatically request the correct characteristics.

It's a different matter for incoming calls. Historically there's
been no method of passing the required call type along the old
analog landline telephone network, because it didn't matter with
the old technology. Now it does matter when a cellular service
is involved in the loop, so the easy way of catering for the new
requirement is to allocate dedicated numbers for each type of
service to cellular devices which might receive such calls. The
OTA characteristics are set up correctly according to the number
being called.

John

[narke]

Post by John Henderson

Post by narke
Hi,
Today I applied a CSD sim card from my local mobile network operator.
Actually, it seemed they don't call it CSD, but call it as fax/data
service. The strange things is that, with each of the sim card, it was
provided with three different phone number, one is voice, the other two
are fax-in/data-out and fax-out/data-in. Could anyone have some
knowledge about this? It sounds to me that fax and csd are seperated.
Thanks in advance.

The OTA (over-the-air) characteristics of the three services are
different. When establishing a connection from the phone, the
phone knows which type of connection is required and will
automatically request the correct characteristics.
It's a different matter for incoming calls. Historically there's
been no method of passing the required call type along the old
analog landline telephone network, because it didn't matter with
the old technology. Now it does matter when a cellular service
is involved in the loop, so the easy way of catering for the new
requirement is to allocate dedicated numbers for each type of
service to cellular devices which might receive such calls. The
OTA characteristics are set up correctly according to the number
being called.
John

Thanks John, the explaination is clear. A related question is: with
the data-in number associated with the sim card, can I establish a data
connect with it from a PSTN modem (connected to a telephone line)? Will
it have any difference with establishing connection from another
cellular device?

One of my colleague told me, I can do it -- establishing data connection
from PSTN modem to a CSD modem -- but can only using analog telphone
line. I don't understadn why analog or digital telphone line matters in
this case. Do you have some knowlege/experience on this?

Again, thank you very much.

[John Henderson]

Post by narke
Thanks John, the explaination is clear. A related question is: with
the data-in number associated with the sim card, can I establish a data
connect with it from a PSTN modem (connected to a telephone line)? Will
it have any difference with establishing connection from another
cellular device?
One of my colleague told me, I can do it -- establishing data connection
from PSTN modem to a CSD modem -- but can only using analog telphone
line. I don't understadn why analog or digital telphone line matters in
this case. Do you have some knowlege/experience on this?

Sorry, I have no experience which would clear this up. And I
wasn't aware there might be a problem.

Hopefully, someone else will know. Are you in a position to
experiment yourself? Here in Australia, cellular operators have
recently dropped CSD capability due to lack of demand.

John

[narke]

Post by John Henderson

Post by narke
Thanks John, the explaination is clear. A related question is: with
the data-in number associated with the sim card, can I establish a data
connect with it from a PSTN modem (connected to a telephone line)? Will
it have any difference with establishing connection from another
cellular device?
One of my colleague told me, I can do it -- establishing data connection
from PSTN modem to a CSD modem -- but can only using analog telphone
line. I don't understadn why analog or digital telphone line matters in
this case. Do you have some knowlege/experience on this?

Sorry, I have no experience which would clear this up. And I
wasn't aware there might be a problem.
Hopefully, someone else will know. Are you in a position to
experiment yourself? Here in Australia, cellular operators have
recently dropped CSD capability due to lack of demand.
John

Sorry to hear that about CSD in Australia. In, China, nowadays it's
also not easy to get the service. I hope they can keep it open until we
finished our device development, that will be used in Europe.

For the cable telephone problem, yes, I have to do some experiments.
Thanks you very much!