eshop@saturn.ucsc.edu (Jim Warner) (04/28/88)
Appologies ahead of time: the discussion below delves into "mere hardware." I haven't seen a discussion of this pass by on this list. "Inside Appletalk" makes some specific recommendations about how to build an Appletalk physical interface. They recommend using a 26LS30 transmitter with +5V and -5V supplies to drive the transformer. They admit that using "standard RS422 components (power supplies of +5 volts and ground)" may be done with some loss of drive capability. My estimate is that using dual supplies over single supplies offers an advantage of about 8 dB. My investigations to date show that Macs and LaserWriters use the recommended drive scheme while Kinetics FastPath gateways and Farallon PhoneNet Star Controllers do not. The signal loss of 1500 ft of 22 ga wire is about 8 dB at 200 KHz. This means that a PhoneNet setup can be that much larger if the attached devices are restricted to Macs and Laserwriters than if K-boxes are included in the network. If a K-box is positioned in the middle of an extended (linear) network the favorable position will tend to make up for the lower output level. My objective is to discover some rules for configuring extended phone net installations that can be guaranteed to yield success without a lot hand tweaking. I must admit that I don't trust the guidelines given in the Farallon literature. I'm not so much interested in hearing stories like "I tried xxx and it worked." Does anyone have any suggestions for e.g. minimum receive level at any point in the network or max attenuation between most distant stations at what frequency? jim warner Sr Development Engineer University of Ca Santa Cruz
Andrew_Palms@UM.CC.UMICH.EDU (05/20/88)
Jim- If you get any answers to your questions about PhoneNET, I'd like to hear them. We've been having the same problems it sounds like you've been having. Andrew Palms LAN Group Manager University of Michigan