Interconnecting classic computers

As I think most of you know, I have a fairly diverse
collection of 
classic computers (I suspect some others do too). 

Quite often I need to transfer data between 2 machines.
Maybe to 
download a file from this PC, which I've in turn downloaded
from a web 
site, to run on one of the classics. Maybe to print out some
listing from 
a classic. Whatever.

My machines vary in size from the pocket computers up to
machines that 
it's not practical to move. They're scattered throughout a
house. They 
are, alas, not in a machine room. Most of the machines (and
all the ones 
I want to consider for this) have an RS232 port, either
built-in or as an 
option (which I have). Most of the machines run kermit. Or I
can simply 
print to the RS232 port on one machine and capture the
incoming 
characters on the other

So, I think the problem reduces to 'how to interconnect
RS232 ports'. let 
me add some constraints : 
 
Must work over a distance longer than the RS232 spec allows
(i.e. the 
answer is probably not 'A long RS232 cable' ). 

Prefereably no cables at all. One solution I've come up with
is to use a 
couple of line drivers and a long cable between them. A long
cable that 
my parents, or the cat, will get tangled up in :-(

No line-of-sight between the machines

Must work at 300 and 1200 baud. 110 and 9600 baud would be a
bonus

I only need one pair of machines linked at a time. I don't
need a 
network. So if the solution involves a radio link, the fact
that there's 
only one channel available would not be a problem. 

Must not make use of any flow control lines on the RS232
port, since some 
of my machines don't support them.

Using classic, or at least repairable, hardwre is a bonus


I said 'RS232'. I mean asynchronous serial, of course . If
somebody 
has a solution for TTL or 3.3V level serial ports, I can
trivially 
convert the signal levels

I've been looking at some of the license-exempt radio
modules, but they 
either are half-duplex or amke use of the flow control lines
(typically 
they buffer <n> bytes internally, then de-assert a
flow control line 
while they pack up that data and send it to the other end).


So far the best I've come up with is to link one machine to
a palmtop 
(HP95LX), then transfer the data to that, carry the palmtop
to the other 
machine and transdfer the data on. It's not ideal, but it
does work.

Any other ideas?

-tony

Dennis wrote:
> It were me, I'd probably look into Bluetooth- or
Zigbee-based serial
> extenders.

I'm not sure about Zigbee, but the useful range of Bluetooth
is very
short.  There are claims of over 30 meters, but as far as I
can tell
that must be under laboratory conditions, e.g. in a faraday
cage.
In the real world, more than about 3 meters line of sight
works poorly,
as does non-line-of-sight at any distance.

Eric

    I'm trying to identify a transistor from an early '60s
vintage radar 
processor panel:

http://sturgeon.css.psu.edu/~mloewen/Oldtech/Pane
ls/Budd-7L.jpg

    The transistor is labeled "GT1890G052", and I
haven't been able to find 
anything on the web.  They're apparently used to switch
3-lead neon 
indicator lamps.


Mike Loewen				mloewencpumagic.scol.pa.us
Old Technology	http://
sturgeon.css.psu.edu/~mloewen/Oldtech/

Mike Loewen wrote:
> 
>     I'm trying to identify a transistor from an early
'60s vintage radar
> processor panel:
> 
> http://sturgeon.css.psu.edu/~mloewen/Oldtech/Pane
ls/Budd-7L.jpg
> 
>     The transistor is labeled "GT1890G052",
and I haven't been able to find
> anything on the web.  They're apparently used to switch
3-lead neon
> indicator lamps.

I found a few cross-refs for GTxx and GTxxxx numbers, but
not specifically for GT1890.
According to these refs, a prefix of "GT" was used
by General Instruments, General
Transistor, and AEI (England).
.. not much help, I know.

Not likely to be very critical though, surely ..figure out
whether they're NPN
or PNP and choose an appropriate breakdown voltage (?). I
wonder if the 3-lead
neon lamps were used to reduce the breakdown voltage
requirements.