> Here's a representative lot:
> <http://cgi.govliquidation.com/auction/view?id=1686038&convertTo=USD>
>
> They have descriptions like "General Dynamics signal
> processor adapter
> assembly" and they all look like circuit boards with a
> regular grid
> and an arrangements of pins placed into the grids. The
> grids are
> divided into areas and sometimes color coded. Does anyone
> have any
> familiarity with them? There are a ton of these on govliq
> right now.
>
> It seems to be some kind of test harness.
The NSN hyperlink links to a page that identifies it as "AN/ALR-69 PECULIAR." The 4920 NSN prefix indicates that it's aircraft maintenance equipment. The AN/ALR-69 Radar Warning Receiver is used in a number of US military aircraft. If that's gold plating in the second photo from the left, these might have some significant recovered metal value.
____________________________________________________________________________________
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On Mon, 5 May 2008 20:55:51 +0100 (BST), Tony Duell wrote:
> [...]
> 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.
> [...]
>
> So, I think the problem reduces to 'how to interconnect RS232
> ports'. let
> me add some constraints :
>
Requirements as I understand them:
1
> Must work over a distance longer than the RS232 spec allows (i.e. the
> answer is probably not 'A long RS232 cable' :-)).
(see <http://www.lammertbies.nl/comm/info/RS-232_specs.html> for an
interesting discussion on cable lengths v.s. data rate - your data
rates spec'ed below indicate that this is not a problem...
2.
> 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 :-(
i.e. no cables hence 1 does not apply
3.
> No line-of-sight between the machines
This excludes optical means.
4.
> Must work at 300 and 1200 baud. 110 and 9600 baud would be a bonus
5.
> I only need one pair of machines linked at a time. I don't need a
> network. [...]
Point-to-point - collision avoidance not required.
6.
> Must not make use of any flow control lines on the RS232 port, since
> some
> of my machines don't support them.
7.
> Using classic, or at least repairable, hardwre is a bonus :-)
8.
> I said 'RS232'. I mean asynchronous serial, of course :-). [...]
9.
> 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).
Does this mean that you require full-dupex?
-------
If 8 is required, you probably have to go with a dual channel, radio
link of some sort. Zigbee is definitely overkill based on 5. A simple
set of transceivers should do the trick. TI and others have parts and
reference designs. However, my experience has been disappointing in
enclosed and partitioned areas with these devices - at least at legal
power levels...
Item 7 makes me think X10. This is a classic data-over-power-line
method that has been around for good number of years. It is generally
used to control lights, sprinklers, intrusion alarms, etc. and uses a
simple protocol. However, it appears to be half-duplex. The info is
out there on the web.
You might want to look at ST's ST7540 and ST7538 which are current
power-line modems and should do what you want. A small micro to buffer
things will probably take care of 6.
Jules Richardson noted:
> Hmm, I've got a deep mistrust of any 'data over the mains'
> technology, but
> might that be an option here? I assume *most* of your systems are
> physically
> plugged into the mains anyway, so it'd meet the ideal requirement
> for no extra
> cabling. Data rates presumably not lightning fast, of course...
I don't think security is of concern here unless you are extremely
paranoid or are transferring prohibited material (e.g. perhaps with
your collection, ASCII kiddy porn to the impact printer :=P).
CRC
ard at p850ug1.demon.co.uk (Tony Duell) wrote:
> > Has anybody ever tried interfacing a modem to a cordless phone handset?
>
> Are cordless phones truely full-duplex, or are they more like
> loudspeaking phones whee a local voice input disables the speaker
> output?
> That is not a problem for voice, of course, but it is for full-duplex
> modems.
Every one I ever had in my hands was full-duplex, and we started with the analogue generation before we went to DECT. Cordless phones are fun anyway, I recently built a remote power controller for use with an analogue Siemens Megaset base station. (The base station in the ground floor, next to my father's desk, is powered all the time, "picking up" the handset energises a relay that switches on mains for our DSL modem and ethernet hub. Handset is next to my desktop PeeCee in the first floor and powered only when my desktop computer is on. The controller of course also has a local switch wired in parallel, for when my father wants to go online.)
> > It shouldn't be too hard to use a C/L phone as the wireless link
> > between two modems.
I'd be very interested in such an arrangement, but I have the suspicion that there will be no convenient location in the handset's circuitry to interface a phone line to.
For the DECT system anyway, there are things called "cordless phone sockets"; they aren't really cordless as they need a wall wart, but they are learned to the base station like a new handset is and present themselves to a phone/fax/modem/whatever like a phone line. Would love to get my hands on one of those one time.
> > I believe Tony also has a NetCommander which would let him select which
>
> Actually I have 3 of them. One is the 16 port model (with 16 RS232
> ports), the others are the fixed-configuration 6 RS232/4 Centronics
> models.
>
> But they do not solce the cabling problem. Nor do they have enough ports
> for all my classics...
I see it's hard to make do without permanent cabling, but the ports shouldn't be such a problem. You could just run two links into each room where you have machines (to a wall socket), then use temporary cables to connect just the machines on which you are working at the moment (either two in one room, or one in one room, one in another - therefore two links).
Cheers,
Arno
--
Arno Kletzander
Student Assistant // Studentische Hilfskraft
Informatik Sammlung Erlangen
www.iser.uni-erlangen.de
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Subject: Interconnecting classic computers
> Quite often I need to transfer data between 2 machines ...
> 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
That's great: that solves the protocol issue and it's all RS232.
> 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.
There are D-I-Y kits for that, and pre-made dongles
for wireless RS232 using bluetooth or Zigbee.
[I got the Circuit Cellar / Freescale Zigbee contest kit
but it failed to flash to the wireless modem program
that I needed for a project]
A "terminal server" puts RS232 ports on ethernet,
but I'm unsure if any have builtin WiFi (802.11)
or are easy to use via WiFi routers/repeaters.
[some are cheap on ebay: I have some but have not
gotten to try them. I used some at a previous assignment].
I saw wireless USB in a catalogue,
so perhaps a wireless USB to a USB-RS232 adapter might work?
I'm suspicious of the USB-RS232 adapters since many are not
8 bit compatible (I learned that the hard way
when one won't download to my PIC-18 development system).
[and most of the USB stuff I've handled lately works under Linux]
> 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 :-(
You're just reinvented the "short haul modem":
a dongle that converts RS232 to stronger signals
to travel longer wires, such as RS485 (differential signalling).
BlackBox sells them for $$$:
http://www.blackbox.com/Catalog/Category.aspx?cid=381,1452,1465
That's why I snagged some fiber optic RS232 adapters:
boxes about the size of a pack of cigarettes that converts
RS232 to fiber optic (up to 1 km).
-- Jeffrey Jonas
Wireless ideas...
Serial-to-Bluetooth modules exist, but they're about $50 the each for
the bare module, which may be too pricey for a large configuration.
Duplex-ness shouldn't be too much of an issue, given a sufficiently
generous buffer.
Diamond MMC had an interesting card back in the 90's that provided
home networking by imposing an RF carrier on the telephone copper
pair. I've still got a couple of these cards and they work pretty
well. The box claims 10Mb/sec, but reality is more like 1Mb. Still
faster than a modem, however.
IR was pretty popular for a short time--you could even go around
corners if you aimed the transceivers right. It sounds as if Tony
just wants to go point-to-point, so there would be only a single
transmitter on at any one time.
Others have mentioned carrier-current setups, but unless they're
pretty sophisticated, low-bandwidth and error-prone. I've got a copy
of an article from an issue of the HP Journal back from the 80's,
where a spread-spectrum carrier current system is described in
detail.
I wonder if one could simply buy a carton or two of old 900MHz
cordless phones and jerry-rig something up? Come to think of it,
I've never even tried interfacing a regular modem to a cordless phone
handset. I wonder if it works...
Cheers,
Chuck
I'm slow to enter the discussion because I'm still
busy sorting my z80 parts and single board systems
instead of enjoying them :-(
I'm of 2 minds regarding the Z80:
The "classic" vs. the "embedded" mind-set.
The embedded solution:
I have a Zilog 50 MHz eZ80 development board with more built-in features
that I may ever use: ethernet, InfraRed,
a LOT of flash and static RAM.
My frustration is the lack of support and community activity
despite some high profile contests using the board.
A clever fellow made an expansion board that adds
2 compact flash slots so it runs CP/M really fast!
That appeals to me since it allows it to run stand-alone
even for editing, storing and compiling applications.
And there's still the programming/debugging pod
for using a host system to debug the system
should it require external assistance.
Back to the original query:
the Zilog ez80 board may be appealing because
- it's fast (50MHz) and has a lot built in:
MMU, RAM, flash ROM, serial and ethernet ports.
- allows much more powerful tools on the host system
for source control, compilers, debugging via the pod.
- others are using it too
The classic side:
My first "at home" computer was a Servo-8 single board computer
(6 MHz Z80B, 64k ram, 2 serial ports, parallel port, SASI port).
I chose that over the 4 MHz Z80A Ampro Littleboard.
It cost about $500 (with CP/M and schematics)
so I was really hesitant to interface it to my own things
until I had some experience with cheaper Z80 systems
(particularly since all the parts were soldered in!)
Long long ago I breadboarded a 4 MHz z80a with 10K static RAM
(intending to use battery backup).
I originally intended to use a front panel of
LEDs and toggle switches (inspired by the Altair).
I gave that up while wiring up all the switches,
and instead used a Timex Sinclair 1000 as the front panel
(hey, a keyboard and display!) to the dual-port static RAM.
(the Timex is a complete Z80 system with just 4 chips:
z80 CPU, ROM, RAM and Programmable Logic Array for the rest).
I still want to use discrete Z80 chips because
- I have a logic analyzer to watch it run
(I've disassembled some embedded z80 terminals using it)
- I like the way the Z80 family chips interface so directly,
even for vectored interrupt mode.
- I still want to explore "clever" tricks for memory management such as
. using the "M" line to differentiate instruction from data reads
. implementing true "cycle stealing"
(access to memory not currently active by the CPU).
I salvaged many z80 based devices (terminals, modems, terminal servers)
and pondered reverse engineering them to reprogram for my own uses.
Perhaps I'm too impatient but it seemed easier to just
start from scratch, or buy a single board system and work from there.
I suspect I'll finally get brave enough to just interface
the additional Z80 chips to the Servo-8 Z80B SBC
since I like that more than the ez80 (so far).
Jeffrey Jonas
e-mail: jeffj at panix.com
>If I plug this hypothetical "just works" serial-to-Ethernet box onto
>a serial port on an old computer, and plug the ethernet into the
>switch along with my desktop computer, laptop, and wireless router,
>what exactly should the box do? And what should I, as the user, do?
RCPMs used a version of XMODEM which worked over the same port as the
console. You would tpye xmodem s/r (send or recieve) and a file name.
XMODEM would then use the console port to upload and download the file.
You would need a xmodem version for the pc which would support a common
protocol.
