JAJZ801@calstate.bitnet (03/03/91)
I would appreciate information on whether a 50-conductor phone cable, presently serving a 1A2 system, would be appropriate for shared use as the wiring of a LAN. Is one use likely to interfere with the other and under what conditions (ringing affect LAN, LAN affect voice or modem calls, etc.) and what could be done to eliminate or minimize these effects. Performance limits on the LAN with such wiring are also of interest. Jeff Sicherman
woody@ucscb.ucsc.edu (Bill Woodcock) (03/05/91)
> I would appreciate information on whether a 50-conductor phone > cable, presently serving a 1A2 system, would be appropriate for > shared use as the wiring of a LAN. Is one use likely to interfere > with the other and under what conditions (ringing affect LAN, LAN > affect voice or modem calls, etc.) and what could be done to > eliminate or minimize these effects. Performance limits on the LAN > with such wiring are also of interest. I commonly run quarter megabit AppleTalk networks over unused pairs in existing building telephone wiring. There are hardware hacks which increase the transmission speed of AppleTalk from 234Kbaud up to 600Kbaud and even one megabit, and having working telephone pairs running in the same cables doesn't seem to affect these either. Both Apple and Farallon (the principal manufacturer of quarter megabit AppleTalk networking components) explicitly state that there isn't a problem with doing this. (The phone lines, not the speed hack!) In addition, most Macintosh-using offices with permanently installed network cabling use the same RJ-13 jack for both voice (inside pair) and AppleTalk (outside pair) which means that they're running side by side on the modular flatwire between the jack and devices, without benefit of pair twisting. I'm more a networking person than an electronics one, but my understanding is that the frequencies used are different enough that crosstalk and induced current aren't a problem. Similarly, 10BASET twisted-pair Ethernet will work in the same situations, for the same reasons, in so far as it works at all. <grin> You need twisted pair drop cables between your walljack and transciever or card with 10BASET, instead of the (easier to terminate) eight-conductor modular flatwire, though. Bill Woodcock BMUG NetAdmin bill.woodcock.iv woody@ucscb.ucsc.edu 2355.virginia.st berkeley.california 94709.1315
alans@hp-ptp.hp.com (Alan_Sanderson) (03/10/91)
Re use of 50 conductor telephone cable for LAN- Starlan-10 (10base-t) was designed specifically for this type of cabling, in order to use existing telephone wiring for data communication. As its name implies, the connections are in a star configuration, with a repeater at the center of the star. It expects to see approx. 100 ohm impedance on the cable, and does not normally interfere with voice traffic because of the frequency difference (5-10 MHz vs. 3 kHz).
alans@hp-ptp.hp.com (Alan_Sanderson) (03/15/91)
Re use of 50 conductor telephone cable for LAN- Starlan-10 (10base-t) was designed specifically for this type of cabling, in order to use existing telephone wiring for data communication. As its name implies, the connections are in a star configuration, with a repeater at the center of the star. It expects to see approx. 100 ohm impedance on the cable, and does not normally interfere with voice traffic because of the frequency difference (5-10 MHz vs. 3 kHz).