Store RS232 data onto tape recorder

Store RS232 data onto tape recorder

Post by Derek Fletche » Fri, 26 Oct 2001 06:59:03



Any ideas on how I could use only ONE external modem to receive rs232 data
and have it modulate the data so that I can output the audio to my soundcard
or tape recorder. I only need 4800 baud. I am thinking I need to use a
signal generator (imitate answering modem carrier)to fake my modem into

audio of two modems negotiating, or just the answering modem. I have
disabled dialtone detect by ATX0 and given it ATN0S37=7 to lock it to 4800
baud and to disable automode. Do I need to also disable handshaking?
OR am I totally out to lunch with my approach?

I also built a circuit to provide enough milliamps to power the rj11 jack
and have tapped into this phone cord to get the audio out. This circuit
enables me to directly connect two modems without using phone system. My
intention was to get two talking and then see if I could get to just the one
modem scenario. Any help would be appreciated.
Derek

 
 
 

Store RS232 data onto tape recorder

Post by Floyd Davidso » Fri, 26 Oct 2001 10:22:22



>Any ideas on how I could use only ONE external modem to receive rs232 data
>and have it modulate the data so that I can output the audio to my soundcard
>or tape recorder. I only need 4800 baud. I am thinking I need to use a
>signal generator (imitate answering modem carrier)to fake my modem into
>staying off hook and doing a carrier detect. My research shows that for v.32

>audio of two modems negotiating, or just the answering modem. I have
>disabled dialtone detect by ATX0 and given it ATN0S37=7 to lock it to 4800
>baud and to disable automode. Do I need to also disable handshaking?
>OR am I totally out to lunch with my approach?

Lunch time.  :-(

A v.34 modem negotiates a connection with another modem at the
distant end, and it takes more than just an answer tone.
Moreover, once they lock up, they are synchronized to each
other, and equipment which can lock onto it and decode either of
the two modems is expensive.

Basically it could be done with a 300 bps (Bell 103) modem (and
even at speeds higher than 300 bps too!), but not by anything
since the Bell 212A 1200 bps modems came out.

Quote:>I also built a circuit to provide enough milliamps to power the rj11 jack

Rj-11 jacks do not consume power.

Quote:>and have tapped into this phone cord to get the audio out. This circuit
>enables me to directly connect two modems without using phone system. My
>intention was to get two talking and then see if I could get to just the one
>modem scenario. Any help would be appreciated.

Generally, modems do not require any voltage on the line to
function.  (If you have one that does, throu it away and buy a
real modem.)

You do know that using an audio tape recorder with FSK tones was
used by several "home" computers back in the 1970's?  It was the
only thing available until inexpensive (well, relatively
inexpensive any way) floppy disks came along.  But even when
floppies were big in size, small in storage capacity, and
expensive to use, they still beat the jacket off using an audio
tape recorder.  And today, floppies have improved, while audio
tapes have not!

--
Floyd L. Davidson         <http://www.ptialaska.net/~floyd>


 
 
 

Store RS232 data onto tape recorder

Post by Franc Zabk » Sat, 27 Oct 2001 07:54:50



put finger to keyboard and composed:

Quote:>Generally, modems do not require any voltage on the line to
>function.  (If you have one that does, throu it away and buy a
>real modem.)

Line powered silicon DAAs are used by USR, Lucent, Conexant, and
PCtel. It seems they are the trend of the future.

What's so inherently wrong with them? Do you object to the fact that
they rob power from the line? If so, then how does that make them any
different from standard telephones?

My only reservation with silicon on the line side is that it is
probably more sensitive to damage that a typical transformer based
DAA. On the positive side, intelligent silicon DAAs would have
software configurable impedances, etc.

-- Franc Zabkar

Please remove one 'g' from my address when replying by email.

 
 
 

Store RS232 data onto tape recorder

Post by Floyd Davidso » Sat, 27 Oct 2001 08:05:51




>put finger to keyboard and composed:

>>Generally, modems do not require any voltage on the line to
>>function.  (If you have one that does, throu it away and buy a
>>real modem.)

>Line powered silicon DAAs are used by USR, Lucent, Conexant, and
>PCtel. It seems they are the trend of the future.

I hadn't realized that it has gotten that bad^H^H^H common!

Quote:>What's so inherently wrong with them? Do you object to the fact that
>they rob power from the line? If so, then how does that make them any
>different from standard telephones?

I don't see that as a problem at all.  But I do like the ability
to use a pair of modems on a dry cable pair.

Quote:>My only reservation with silicon on the line side is that it is
>probably more sensitive to damage that a typical transformer based
>DAA. On the positive side, intelligent silicon DAAs would have
>software configurable impedances, etc.

Is that positively of any value at all? :-)

--
Floyd L. Davidson         <http://www.ptialaska.net/~floyd>

 
 
 

Store RS232 data onto tape recorder

Post by Franc Zabk » Sun, 28 Oct 2001 10:09:23



put finger to keyboard and composed:

Quote:>>My only reservation with silicon on the line side is that it is
>>probably more sensitive to damage that a typical transformer based
>>DAA. On the positive side, intelligent silicon DAAs would have
>>software configurable impedances, etc.

>Is that positively of any value at all? :-)

I don't know. I was hoping you would be able to tell me.

I notice that the homologation commands for Lucent modems and the
Silicon Labs datasheets allow a choice of real or complex impedances.
One or the other is automatically selected when you configure your
modem for a particular country. I would have thought that correct
impedance matching of the phone line would be advisable (necessary ?)
for an optimal connection.

-- Franc Zabkar

Please remove one 'g' from my address when replying by email.

 
 
 

Store RS232 data onto tape recorder

Post by Floyd Davidso » Sun, 28 Oct 2001 10:51:49




>put finger to keyboard and composed:

>>>My only reservation with silicon on the line side is that it is
>>>probably more sensitive to damage that a typical transformer based
>>>DAA. On the positive side, intelligent silicon DAAs would have
>>>software configurable impedances, etc.

>>Is that positively of any value at all? :-)

>I don't know. I was hoping you would be able to tell me.

oh.  shucks...   I donno! :-)

Quote:>I notice that the homologation commands for Lucent modems and the
>Silicon Labs datasheets allow a choice of real or complex impedances.
>One or the other is automatically selected when you configure your
>modem for a particular country. I would have thought that correct
>impedance matching of the phone line would be advisable (necessary ?)
>for an optimal connection.

If all that ever happens is a one time option setting of this or
that it can't be worth much.

The primary value in having a good impedance match is to reduce
echo.  But since software driven echo cancellation is used, and
is far more effective than any kind of simple impedance matching,
I doubt that it makes any difference at all with today's modems.

--
Floyd L. Davidson         <http://www.ptialaska.net/~floyd>

 
 
 

1. Store Modulated Data onto tape recorder

Any ideas on how I could use only ONE external modem to receive rs232 data
and have it modulate the data so that I can output the audio to my soundcard
or tape recorder. I only need 4800 baud. I am thinking I need to use a
signal generator (imitate answering modem carrier)to fake my modem into

audio of two modems negotiating, or just the answering modem. I have
disabled dialtone detect by ATX0 and given it ATN0S37=7 to lock it to 4800
baud and to disable automode. Do I need to also disable handshaking?
OR am I totally out to lunch with my approach?

I also built a circuit to provide enough milliamps to power the rj11 jack
and have tapped into this phone cord to get the audio out. This circuit
enables me to directly connect two modems without using phone system. My
intention was to get two talking and then see if I could get to just the one
modem scenario. Any help would be appreciated.
Derek

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