4 Dec
2011
4 Dec
'11
2:59 p.m.
Tony Duell wrote:
[1] An old Miracle WS2000, the black box with 3 knovbs
on the front that
weas commonly used with the BBC micor. It's an AM7910 and not much else,
I like it because it can be controlled from the front paenl rotary
swiches, and I Know exactly waht it's going to do. Since I only use it on
a private system (my line simulator), I've eneabled the Bell modes by
remove the pin from the rotary switch. I'd love to find the autodial and
answer boards for it, but no chance...
There's also a kit (SK-1) to add a few parts which allow full software
control. Miracle Technology used to scrape off the IC type numbers in a
vain attempt to prevent people working out what they were, and as you
can imagine I immediately decided to work out what they were. Diagram
available if required :-) along with the original MT documentation.
One problem you sometimes find when the SK-1 kit and/or
autodial/autoanswer boards are fitted is that the internal 5V line gets
very noisy, and the modem does odd things due to switching glitches.
Really only a problem if you install SK1. Thin tracks and small
smoothing capacitors around the regulator are the problem, easy fixed
with a little extra wire and a couple of caps.
Actually I might have a spare autodial board. Originally there was
supposed to be a single autodial-autoanswer (AA1) board but that was
withdrawn because of trouble with BABT. Later came separate autodial
(AD2) autoanswer (AA2) boards and I remember both being quite simple.
AD2 needed the software control kit (the older board didn't, it was
entirely controlled by the DTR line) but the AA2 didn't. I worked out
schematics for some of them, but the autoanswer board I built and used
worked in a slightly different way, using "ringback".
"Ringback" was a technique to allow use of a modem for a dial-in BBS (or
whatever) without preventing normal use of a domestic phone line. If
the phone rang, the modem detected that and set a flag. If it went on
ringing (usually for two or more rings) the flag was cleared, and the
modem ignored it, so mortals could call the (house) number as normal.
If the modem detected just one ring, and then a gap (10 seconds or so),
and then more ringing, it would answer. So a BBS user would dial, hang
up quickly, and redial, to get connected. Ordinary mortals would just
dial and let the phone ring as usual.
Can't help much with the Tantel, I'm afraid. I did some work with
SoftMachinery for Acorn's Prestel ROM, and although I used to have the
source for the Tantel driver (called "tantrum" because of its
"reliability") I can't find it now. I used WS2000s and wrote drivers
for those ("madam", because it could be a little m.. with some version
of the ROM code).
--
Pete Peter Turnbull
Network Manager
University of York