28 Jan
2014
28 Jan
'14
2:17 p.m.
On Jan 28, 2014, at 3:37 PM, Eric Smith <spacewar at gmail.com> wrote:
On Jan 28, 2014 12:53 PM, "Paul Koning"
<paulkoning at comcast.net> wrote:
Asymmetric, or full duplex four wire. The PLATO case was two wire, with the ?secondary?
reverse channel on the same wire at slow speed. 75 bps sounds plausible.
paul
Similarly, they would not care about sync vs.
async. PLATO used Bell 202
modems for 1260 bps 21 bit sync one way, slow speed
(50-100 bps?) 10 bit
plus parity async the other way, on a standard 2 wire phone link.
Bell 202 was asymmetric with provision for line turnaround. 1200/75 was
common. I doubt 1260 would pose any problem, but I'm not sure how much you
could push the slow direction. What could be achieved in practice with 202
(or any FSK modem) was more limited by the performance of the specific
modems than the theoretical limit of the FSK modulation, bandwidth, and
channel SNR.