Re: 300baud FSK over GSM

From: Hans-Bernhard Broeker (broeker_at_physik.rwth-aachen.de)
Date: 09/30/04 

Date: 30 Sep 2004 12:02:30 GMT

[Note: F'up2 list cut down --- should have been done by OP]

In comp.arch.embedded Denis Gleeson <dgleeson-2@utvinternet.com> wrote:

> Essentially the requirement comes from the fact that the equipment
> at the far end can only communicate at 300baud FSK over the PSTN
> network.
> We are connecting a board to this equipment which will have a GSM
> module (modem) on it.
> Our end will be a standard PC with a PC modem(connected to PSTN)."

Sorry, but I think this clarified version actually makes no more,
possibly even less sense than the original.

In a system of three devices, all of them being a modem, something
can't be right --- you'll eventually end up with a loose end that is a
telephone jack connected to nothing.

> What I am thinking following the discussion here is that I need to
> take my 300baud FSK and convert it to a digital data stream (using
> Microprocessor and zero crossing detector) and use the data
> communication capabilities of my GSM modem to send the data to my PC
> modem.

Yes. In the effect, you need a bona fide 300 Bd modem, and no, a GSM
phone's audio in/out can't be used in that function. You may also
need a PSTN line simulator --- a simple pair of cables won't do, IIRC.

Then you'll need a micro that connects to both this modem and your GSM
modem. That will *not* use any PSTN modem standard, though, but
rather a digital-only transmission method (SMS, CSD, HSCSD, GPRS,
...). If you have that thing call a PSTN number in data mode, then
the GSM provider will indeed have to convert from GSM digital to
analog signals.

Which thus drives the total number of modems involved in this scenario
to a rather crazy 6:

* 3 at the location of that remote device-thingy
* 2 somewhere in the GSM provider's infrastructure
* 1 at your PC's location

Are you *sure* getting a PSTN land line to that remote device's
location wouldn't be a whole lot less hassle? 

-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Relevant Pages

  • Re: 300baud FSK over GSM
    ... > We are connecting a board to this equipment which will have a GSM ... > Our end will be a standard PC with a PC modem(connected to PSTN)." ... modem or is essentially a GSM phone that contains Hayes Compatible one (e.g. ...
    (comp.arch.embedded)
  • Re: 300baud FSK over GSM
    ... > We are connecting a board to this equipment which will have a GSM ... > Our end will be a standard PC with a PC modem(connected to PSTN)." ... modem or is essentially a GSM phone that contains Hayes Compatible one (e.g. ...
    (sci.electronics.design)
  • Re: 300baud FSK over GSM
    ... > We are connecting a board to this equipment which will have a GSM ... > Our end will be a standard PC with a PC modem(connected to PSTN)." ... In a system of three devices, all of them being a modem, something ... > communication capabilities of my GSM modem to send the data to my PC ...
    (sci.electronics.design)
  • Re: 300baud FSK over GSM
    ... at the far end can only communicate at 300baud FSK over the PSTN ... Our end will work with GSM and needs to communicate at the 300 baud ... We are connecting a board to this equipment which will have a GSM ... module (modem) on it. ...
    (sci.electronics.design)
  • Re: 300baud FSK over GSM
    ... at the far end can only communicate at 300baud FSK over the PSTN ... Our end will work with GSM and needs to communicate at the 300 baud ... We are connecting a board to this equipment which will have a GSM ... module (modem) on it. ...
    (comp.arch.embedded)
Loading