It hasn't been mentioned so: Localtalk is essentially an RS485 standard connection. Apple adds transformers and a modulation scheme (FM0) that makes use of the ground isolation that the transformers provide. They have been called "pulse transformers" here but they are really broad band units supporting a few kHz to 250 kHz. They do not saturate like the pulse transformers used for triacs and flash photography.
But the transformers are not necessary if the various computers are pretty much in the same environment - connected to the same power circuit in the same house with three wire plugs for instance. It's quite possible to connect the RS422 transmitters directly to the wire pair that constitutes the bus. The RS422 receive lines are best connected to the same bus with a pair of, say, 1 kiloohm series resistors to avoid overloading the receivers. For one-to-one localtalk a standard Apple serial connector - as for an Apple RS422 modem - will work. The only other things you need are two 110 ohm resistors shorting the open ends to the bus to provide termination. Shielded audio twisted pair is good stuff to use. -- --> There are 10 kinds of people: those who understand binary, and those who don't <-- -- Compact Macs is sponsored by <http://lowendmac.com/>. Support Low End Mac <http://lowendmac.com/lists/support.html> Compact Macs list info: <http://lowendmac.com/lists/compact.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/compact.macs%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
