30 Dec
2007
30 Dec
'07
11:59 a.m.
Hi list,
I have two "Compaq Enhanced II Keyboard"s here (they look old enough
to be on-topic) - PS/2 connector, but they don't work on any PC I've
tried them with.
Are these specific to one machine? If so, is there any interest before
I dumpster them?
Thanks,
Ed.
30 Dec
30 Dec
12:52 p.m.
New subject: Modem to Modem without a line simulator?
This question is bugging me from another forum.
Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able to
communicate?
I always thought that this can not work because the line that the modems
are connected to has to have some current. The phone system works
because an action on one end of the phone (talking into the carbon
microphone) causes a reaction on the other end. Without some sort of
current on the line, how can this work? Hence the need for 'line
simulator' circuits
Some people are claiming that it works without the line simulator. I'd
like to understand why.
(I could get out the multimeter if things get really desperate, but
maybe somebody can tell me that the line current thing only applies to
acoustically connected modems, not direct connect. Or the direct
connect modems put enough juice on the line to make it work. Or
something else that might make sense.)
1:38 p.m.
New subject: Modem to Modem without a line simulator?
From: mbbrutman-cctalk at brutman.com
This question is bugging me from another forum.
Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able to
communicate?
I always thought that this can not work because the line that the modems
are connected to has to have some current. The phone system works
because an action on one end of the phone (talking into the carbon
microphone) causes a reaction on the other end. Without some sort of
current on the line, how can this work? Hence the need for 'line
simulator' circuits
Some people are claiming that it works without the line simulator. I'd
like to understand why.
(I could get out the multimeter if things get really desperate, but
maybe somebody can tell me that the line current thing only applies to
acoustically connected modems, not direct connect. Or the direct
connect modems put enough juice on the line to make it work. Or
something else that might make sense.)
Hi
The only thing missing that might be a problem is that
there is no ring generator. If you force the modems
to be off the hook, they could be just connected together.
The current is used for the carbon mike and to tell the
phone system that the phone is off the hook. Line connected
modems don't have any use for the current and only have
a load resistor there to keep the line connected.
Other than the ring detect, there is no reason two
modems can't talk to each other since they are self powered.
Dwight
_________________________________________________________________
Don't get caught with egg on your face. Play Chicktionary!
http://club.live.com/chicktionary.aspx?icid=chick_wlhmtextlink1_dec
3:56 p.m.
New subject: Modem to Modem without a line simulator?
On Sun, 2007-12-30 at 13:38 -0800, dwight elvey wrote:
Other than the ring detect, there is no reason two
modems can't talk to each other since they are self powered.
Some modems detect loop current and won't play unless there's something
there. You can use a 9v battery to provide this.
Gordon
4:02 p.m.
New subject: Modem to Modem without a line simulator?
On Sun, 30 Dec 2007 23:56:40 +0000, Gordon JC Pearce wrote:
On Sun, 2007-12-30 at 13:38 -0800, dwight elvey wrote:
> Other than the ring detect, there is no reason
two
> modems can't talk to each other since they are self powered.
Some modems detect loop current and won't play
unless there's something
there. You can use a 9v battery to provide this.
Gordon
and if you want to create a ring, 90vac at 30 cps works just fine :-)
later
the other Bob
4:44 p.m.
New subject: Modem to Modem without a line simulator?
dwight elvey wrote:
And, in fact, one of the AT commands initiates negotiation without a
ring. I disremember which one, but I've used 2 modems and a "plain
vanilla" 4-wire phone cord between them.
Doc
From:
mbbrutman-cctalk at brutman.com
This question is bugging me from another forum.
Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able to
communicate?
Other than the ring detect, there is no reason two
modems can't talk to each other since they are self powered. 
5:12 p.m.
New subject: Modem to Modem without a line simulator?
On Dec 30, 2007 6:44 PM, Doc Shipley <doc at mdrconsult.com> wrote:
And, in fact, one of the AT commands initiates
negotiation without a
ring. I disremember which one, but I've used 2 modems and a "plain
vanilla" 4-wire phone cord between them.
ATA[nswer] on one and ATO[riginate] on the other should do the trick.
1:49 p.m.
New subject: Modem to Modem without a line simulator?
At 11:52 AM 12/30/2007, you wrote:
This question is bugging me from another forum.
Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able
to communicate?
I always thought that this can not work because the line that the
modems are connected to has to have some current. The phone system
works because an action on one end of the phone (talking into the
carbon microphone) causes a reaction on the other end. Without some
sort of current on the line, how can this work? Hence the need for
'line simulator' circuits
Some people are claiming that it works without the line
simulator. I'd like to understand why.
(I could get out the multimeter if things get really desperate, but
maybe somebody can tell me that the line current thing only applies
to acoustically connected modems, not direct connect. Or the direct
connect modems put enough juice on the line to make it work. Or
something else that might make sense.)
I've done it with a Hayes 1200 and a Hayes Supermodem 28.8. I think
I may have done it with a Hayes 300 in an Apple IIe.
I don't know how it works, but it did...
2:08 p.m.
New subject: Modem to Modem without a line simulator?
"Michael B. Brutman" wrote:
This question is bugging me from another forum.
Is it possible to connect two modems (eg: Hayes 2400 to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able to
communicate?
I always thought that this can not work because the line that the modems
are connected to has to have some current. The phone system works
because an action on one end of the phone (talking into the carbon
microphone) causes a reaction on the other end. Without some sort of
current on the line, how can this work? Hence the need for 'line
simulator' circuits
Some people are claiming that it works without the line simulator. I'd
like to understand why.
(I could get out the multimeter if things get really desperate, but
maybe somebody can tell me that the line current thing only applies to
acoustically connected modems, not direct connect. Or the direct
connect modems put enough juice on the line to make it work. Or
something else that might make sense.)
Yes, it will work (or can, acknowledging the idiosyncrasies of some modems) (I
have used it on occasion to transfer between machines that had no other common
communication/IO facility).
You're on the right track about the modems putting juice on the line. The
original design of the phone system, as you suggest, was such that the carbon
mike modulated the DC line current to produce an AC component (the audio) on
the line, the carbon mike acting as a variable resistance and the DC line
current being the only source of energy on the line.
However, many directly-connected modems are transformer coupled onto the line
and actually inject their own AC energy onto the line, with no inherent need
for the DC line current.
On the other hand, some modems (generally later, higher-speed ones, I believe)
use opto-isolator-coupling onto the line and so work more like the carbon mike,
and will require the DC line current.
It's been awhile since I've done it, but the general idea is to simply connect
up the modems (one pair/two wires), set one into answer mode (ATA), and set
the other into originate mode (ATD or ATH1(?)), forcing one/both off-hook.
10:23 p.m.
New subject: Modem to Modem without a line simulator?
It might also be worth noting that some modems are capable of
operating as line drivers and require only a dry pair between them to
function.
--
Golan Klinger <gklinger at gmail.com>
Dark is the suede that mows like a harvest.
31 Dec
31 Dec
12:44 a.m.
New subject: Modem to Modem without a line simulator?
Is it possible to connect two modems (eg: Hayes 2400
to Hayes 2400)
using a 'dead' or isolated pair of copper wire and have them be able
to communicate?
It depends on the modems. Some modems refuse to try to talk unless
they see dialtone and/or battery voltage. Others can be told to ignore
such deviations from normal PSTN operation and try to operate anyway.
(It's possible that some modems that appear to be in the first class
are actually in the second and just don't document it.)
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10 comments
11 participants
participants (11)
-
caveguy＠sbcglobal.net -
dkelvey＠hotmail.com -
doc＠mdrconsult.com -
gklinger＠gmail.com -
gordonjcp＠gjcp.net -
grant＠stockly.com -
hilpert＠cs.ubc.ca -
listmailgoeshere＠gmail.com -
mbbrutman-cctalk＠brutman.com -
mouse＠Rodents.Montreal.QC.CA -
silent700＠gmail.com