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Appletalk/Phonenet box wiring (Re: ...phoneNet connection to Win2K?)
- Subject: Appletalk/Phonenet box wiring (Re: ...phoneNet connection to Win2K?)
- From: mister_boffo@hotmail.com (Mister Boffo)
- Date: Mon, 09 Jul 2001 06:39:07 GMT
- Newsgroups: comp.sys.apple2
- Organization: CenturyTel.Net
- References: <LyQ07.93955$Mf5.27169067@news3.rdc1.on.home.com>
- Xref: archiver1.google.com comp.sys.apple2:10162
On Thu, 05 Jul 2001 02:47:07 GMT, "Tim Haynes"
<trhaynes@yahoo.SPAMBGONE.com> wrote:
>Hey gang,
>
>I have a IIgs that is currently using Appletalk over a
>Localtalk connection (actually phoneNet connectors that I
>scrounged up). One of my phoneNet connectors is kinda weird -
>it has a 9pin serial connection (perfect for a Windows COM
>port) that is plugged into an adapter to bring it back to the
>Mac printer port (geez, I'm out of the loop! What are those
>connectors called again? DIN? DB9? Grrr... memory fading...).
The Mac connector is RS-422, the PC is RS-232.
However, this does not mean a connection is impossible. The
actual network is merely two wires run in parallel from machine
to machine, in a "Bus" architecture. That fat little box
contains a transformer and a bunch of noise filtering components
to interface the bus with the serial in/out ports.
The main difference between the cheaper Phonenet and expensive
Appletalk boxes is what is known as "termination". The ends of
the network need to have a resistor connecting the signal to
ground. The resistor dampens noise and signal reflections in
the wire.
Appletalk is self-terminating. By default both ports on an
unused box are already terminated. The network cable, when
inserted into the box, physically presses back on a switch,
and the switch disconnects the terminating resistor for that
port. Pull out the cable, and the resistor reconnects. Very
slick. Probably why Apple always charged $75 and up for that
seemingly useless little box.
Phonenet requires manual termination. You have to stick a
little phone plug into the spare port, and the plug is wired
with a resistor. Now, it WILL work without termination, but
likely only with short runs between 2-6 machines in the same
room. If you plan to span the network 1000 feet or so,
termination is very important.
And would ya know it, I've got a disassembled Appletalk dongle
right here. Wiring looks like this inside:
T1
BUS Wire 1 --+------+--- ----------+--------- Serial Red
| | ) ## ( |
Term R2 | ) ## ( `--- R4 -- Serial Blu
| | ) ## (
Term Sw | ) ## (
| | ) ## (
BUS Wire 2---+----- | -- ## --- N/C
| ) ## (
| ) ## (
R1 ) ## (
| ) ## ( .--- R3 -- Serial Wht
| ) ## ( |
BUS Ground----------+--- ----------+--------- Serial Grn
|
|
`-----------+-- R5 --+-------- Serial GND
| |
`-- C1 --'
(noise filter)
Okay, I don't know what the serial wire colors represent but
it seems fairly easy to figure out. The main thing you need to
know about RS422 is that you might say the sending line has
its own ground, and so does the receiving line. It's usually
represented as RX+ RX- and TX+ TX-
In order for you to send a signal you have to send from RX+
through the transformer and out to RX-. Similarly to receive
a signal the transformer must connect to TX+ and TX-.
What they have done is tie BOTH signal lines together. So
basically the input is automatically receiving whatever is
output to the network.
I would not be suprised to see that R3 is dampening RX+ and
R4 is dampening RX- to keep it from being overloaded by the
local signal transmissions on that same machine.
Conversion to a PC serial is a problem since the power in
the serial port typically flows like this:
Sending from PC1 to PC2 Sending from PC2 to PC1
TX -->>>-- RX TX ------- RX
PC1 PC2 PC1 PC2
GND --<<<-- GND GND -->>>-- GND
RX ------- TX RX --<<<-- TX
Ground is multidirectional, balancing the current flow of
the various signal lines traveling in either direction.
One option is the following. With this, Serial TX flows to
local ground, completing the circuit. Meanwhile when a
network signal is received, power flows from ground to
Serial RX, keeping the polarity the same:
T1
BUS Wire 1 --+------+--- ----------+--------- Serial TX
| | ) ## ( |
Term-R2 | ) ## ( `--- R4 -- N/C
| | ) ## (
Switch | ) ## (
| | ) ## (
BUS Wire 2---+----- | -- ## -------------------- GND
| ) ## (
| ) ## (
R1 ) ## (
| ) ## ( .--- R3 -- N/C
| ) ## ( |
BUS Shield----------+--- ----------+--------- Serial RX
|
|
`----------+-- R5 --+------ Serial Shield
| |
`-- C1 --'
(noise filter)
I don't really know if this would work. Can you think of any
better possible wiring schemes?
-------------------------------------------------------------
PHONE-NET box:
Hey, wouldn't ya know it, I got one of those too. :)
.-- R3 -- Ser Org
T1 |
BUS 1 -----+-------------- -------+-------- Ser Brn
| ) ## (
| ) ## (
| ) ## (
BUS 2 ---- | ---------+--- -------+-------- Ser Red
| | |
+---. +---. `-- R4 -- Ser Blk
Filter | | | | Filter
for R1 C1 R2 C2 for
BUS 1 | | | | BUS 2
| | | |
`---+------+---+------------------ Ser Shield
Hmmm, looks a little familiar. Same transformer layout. Only
real difference is the filtering. I would have to guess that
the extra filtering is needed because these cables are not
shielded at all, being plain phone cord.
On another front, I have found that Phonenet and Appletalk
are so similar that you can just wire the two together
without any harm. Take an Appletalk BUS cable and hack it
off. Take a phonenet cord and hack it off. Connect the two
outer wires of the phonenet cord and attach them to the bus
cable wires. Tape it together, and plug it in.
-Mr. Boffo