Xref: utzoo comp.protocols.appletalk:5054 comp.sys.mac.comm:2161 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod!pacific.mps.ohio-state.edu!linac!att!pacbell.com!ucsd!ucbvax!agate!darkstar!ucscb.UCSC.EDU!woody From: woody@ucscb.UCSC.EDU (Bill Woodcock) Newsgroups: comp.protocols.appletalk,comp.sys.mac.comm Subject: Re: do I need phone net connectors? Message-ID: <11058@darkstar.ucsc.edu> Date: 15 Jan 91 00:31:17 GMT References: <1991Jan8.090043.25113@sics.se> <1991Jan8.112500.14143@d.cs.okstate.edu> <1991Jan9.175029.23835@sics.se> Sender: usenet@darkstar.ucsc.edu Followup-To: comp.protocols.appletalk Organization: University of California, Santa Cruz Lines: 50 >> Actually, the main reason for using a LocalTalk transciever >> box like a Farallon PhoneNet connector is to prevent your >> SCC chip and potentially your motherboard from being fried >> by static and higher-than-5v-charges coming in off the >> printer port. >> LocalTalk transcievers by and large do two things: >> they combine the T+ and T- and R+ and R- onto a single >> balanced pair, and they provide surge suppression and >> protection from voltage spikes. >> >> -Bill Woodcock >> BMUG NetAdmin > The transformer inside the LocalTalk transciever box is > isolating from DC current but static will be like AC. The > transformer will happily give it to your SCC chip. Or is the > transformer to small to transfer that much energy or to slow > for responding to static? > > Kent Boortz > boortz@sics.se The transformer is there to balance and match the impedance of the conductors to that of the network device's serial port. It provides a minimal level of protection from surges and spikes. In addition, there's a spark gap to the serial port's ground, so any voltage over and above what the transformer can take care of will gap across to the ground. This design is the one used by Farallon in both their PhoneNet Connectors and StarConnectors, and is similar to the one used by NeuvoTech in their clone. Some of the other brands don't contain the spark gap. -Bill Woodcock BMUG NetAdmin _______________________________________________________________________________ 0000 : 0600 0800 7700 FE00 FF 0 FF8 7F 0 3 00 48 bill.woodcock.iv 0010 : CC00 7C00 0C00 1000 2800 440 8200 40 0020 : C000 4000 8000 C000 C 00 800 80 48 0 9 woody@ucscb.ucsc.edu 0030 : FF00 F000 7F80 CC00 CC 0 7 80 7 80 CC 6 0040 : CC00 7F80 9800 7800 CC00 CC0 CC 0 C 00 2355.virginia.st 0050 : CC00 CC00 FC00 CC00 CC 0 2000 10 0 7 00 C 0 0060 : CC00 CC00 CCC0 4800 2 00 1 00 2 00 48 0 9 berkeley.california 0070 : 4800 2400 1200 1000 2800 4 00 8 00 E0 0080 : 3000 6000 F000 6000 000 60 0 600 C0 0 01C 94709.1315 _______________________________________________________________________________