Druckerkabel als Netzwerkkabel?CapNet Info
Druckerkabel als Netzwerkkabel?
From Patrik_Schindler@og.maus.de (Patrik Schindler)
Subject: Re: AppleTalk nicht mit Druckerkabel?
FW> Habe gerade bei den Tips gelesen, dass man
FW> zwei Macs nicht ueber ein einfaches Druckerkabel
FW> direkt vernetzen soll. Warum nicht?
Potentialunterschiede.
Ich hatte zu meinem Nachbarn mal eine Leitung liegen. Wenn der seine (elektische) Heizung eingeschaltet hatte, waren maximal 1200 bps auf der Schnittstelle möglich, alles andere hat zuviele Fehler verursacht. Schlimmstenfalls kann bei sowas ein Schnittstellenbaustein abrauchen, da die Unterschiede je nachdem bis zu einigen -zig Volt ausmachen können. Das Problem tritt definitiv nicht auf, wenn beide Macs an der selben (Wand)steckdose oder zumindest an der selben Sicherung hängen. Ausserdem, was kosten denn heute noch zwei PhoneNet Böxli? :-) (Die haben einen Trenntrafo drin, der das Problem eliminiert)
Netzwerkkabel im Selbstbau
Das CapNet funktioniert ähnlich wie die Phonenetverbindung. Zwei genial primitive Platinen und ein einfaches Telefonkabel. Ich habe es ausprobiert und es funktioniert einwandfrei. Nebenwirkungen sind bisjetzt noch nicht aufgetreten. Von Nate Hawthorn, ergänzt durch Christopher Ferebee
Im Internet unter at-connector-substitute.txt zu finden
Info on connecting to HP DeskWriter added 10/Feb/92 by Christopher Ferebee
What is it?
By Nate Hawthorn (Mr. 6502) 7/20/90
CapNet is a simple low cost network for AppleTalk.
CapNet was designed because network connectors are too simple to cost so much. You can spend $20 to $70 for each connector, and you need at least two. That's min $40! You could have a nice couple of nights out for that!
CapNet was designed for small local networks of up to 10 nodes (further testing may up that number). I have tested it to about 400 ft ! (and it still looks good on the scope)
CapNet costs about $1 in parts (depending on what you may have on hand and what swap meet you go to). Two connectors can be assembled in about a 1/2 hour.
It's so simple and cheap that you'll never see it retailed.
CapNet has a few limitations
You must use CapNet only where the GROUNDS of all the computers are the same (within reason). Like a single office, building or home. It is not designed to connect to the other office across the street, or your neighbor's house. (it doesn't actually use the ground, and is isolated)
There is built in protection that can isolate you from possible damage.
WARNING: YOU WILL ONLY BE TOLD THIS ONCE... DO NOT USE THIS IF YOU ARE RUNNING IT TO OTHER BUILDINGS THAT USE A DIFFERENT GROUND. CHECK WITH A QUALIFIED ELECTRICIAN IF YOU ARE NOT SURE, THEY WILL PROBABLY NOT CHARGE FOR THIS. READALL THE TEXT HERE.
Disclaimer: USE OF THIS DEVICE IS STRICTLY UP TO YOU, IT IS FOR EXPERIMENTAL PURPOSES ONLY. BY IT'S USE YOU AGREE NOT TO HOLD ANYONE LIABLE FOR ANY DAMAGE FROM THE USE OF THIS DEVICE.
You may also notice RF interference on your portable phone or radio. Use shielded cable wherever possible and make sure you are using TWISTED PAIR wires, some phone wire is not twisted inside. If you get interference on your phone line, use a separate twisted pair cable.
However, you can read the reports of people who have used this to their delight!
TESTING CapNet
Once you have built two units (and I don't have to tell you how) set your ohm meter to about 20K and measure across J2, it should show nothing. Measure across RCV(-) and RCV(+), it should show about 2K. Measure across TX(-) and TX(+), it should show about 2K. Measure between any pin and GND, it shouldn't show any less than 1K. If any of these tests fail, simply look for shorts.
To test, connect up two Macs (go borrow one) via a short two wire cable. AppleTalk uses the "Printer" port. Install the "Public Folder" program into the system folder, it should be available on this BBS (I try to upload it wherever possible, it's free to Claris users). Make a new folder in the main directory called "Public" and put some files in it. Restart both Macs and select "Chooser" in the Apple menu. Turn on AppleTalk and select the Public Icon.
You should then be able to copy files from one computer to the other. You can even do it while the other computer is downloading a file from a BBS !
If it doesn't work go back and check for shorts (above). The polarity of the two wire connection doesn't mater.
QUICK HOW IT WORKS
The original AppleTalk connector uses a transformer for isolation and has some RFI circuits built in. This is great for networks to other buildings.
CapNet uses capacitors (hence the name "Cap") to isolate small surges and isolate the cable.
AppleTalk turns off it's IC drivers when it's not sending, this allows data to come into the receivers.
The problem with just hooking the ports up straight is that two computers can "collide" and transmit at the same time. Since the burst time is short (3 to 4 uS) and since several feet of wire has resistance, this would really not be a problem. However, CapNet includes resistors just incase the real world sneaks up on it. The resistors to ground keep static from building up on the twisted pair cable.
Pretty simple huh ?
CREDITS
You can build as many as you want, as long as you don't sell them retail (you can charge your friends a small fee).
This text can be distributed far and wide, and as with all things like this, give credit where credit is due (include my name). KEEP ALL PARTS OF THIS TEXT TOGETHER
Please take a little bit of time and tell me how you used CapNet and what you connected it to. I would like to know how many people I helped. I can be reached on America On Line or the Space Sciences BBS Calif.
STUFF
Also, can anyone take the nice idea that Claris came up with ("Public Folder") and make it act more like "Tops". So that you don't have go to chooser to access another computers folder ? If that was put in the public domain, networking would be very reasonable indeed !
Can you imagine all Mac owners having a network for near nothing, and all the IBM'ers having to pay $200 for some board (they always say the Mac is too expensive).