harkins (03/17/83)
for really long runs of rs 232, there are some new rs 232 fiber optics extended line units that i've seen in Computer Design recently; anybody try one yet? btw, MacNamara's "Technical Aspects of Data Communicatons," from DEC press, has some neat charts that supposedly say what you can expect from a couple of different kinds of cabling as to distance and speed; in general though, the better the cable, the further you can violate the rs 232c spec; i use Belden 8777 reliably to 300 ft. at 9600, which incidentally seems to tally with MacNamara's upper limit. ribbon cables also have a problem of no shielding typically, which doesn't help; i found one of our users, who had a "bad" modem, had managed to pass the ribbon cable from modem to terminal, right between the AC outlets, picking up lots of garbage; never had that arise with shielded wire, but those ribbon jobs are sure easy to make... ernie harkins