Compaq "Enhanced II Keyboard" - what's with these?

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.

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.)

> From: mbbrutman-cctalkbrutman.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=c
hick_wlhmtextlink1_dec

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... 

"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.

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

On Dec 30, 2007 6:44 PM, Doc Shipley <docmdrconsult.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.

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 <gklingergmail.com>
Dark is the suede that mows like a harvest.

> 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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