At 22:00 -0600 12/21/06, Jules wrote:
>Yes, but they're *there* for a lot of products, whether you want them or not.
>If they're not there, and are optional extras, and you pay an additional fee
>for them if you want them, fine.
This is a bit unusual, but there are cases where the added features
make it impossible to use the product. Cell-phone cameras are a case
in point. There are places I work where I would not be allowed to
carry a cell phone which has a camera. Mine doesn't, so I'm OK.
Then there are cases (in software, usually) where an "added feature"
means an entry point for abuse/breakage .... that affects more people.
<busy erasing Spam at the moment....>
--
Mark Tapley, Dwarf Engineer
(I haven't cleared my neighborhood)
210-379-4635 Dwarf Phone, 210-522-6025 Office Phone
Dunno if anyone on the list is into Multibus II gear, but if you are you
might want to grab this one:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190064943671
It's not a VME card, it's a 68030 Multibus II card. Very unusual. He's got
a few other more pedestrian M-II card as well.
Ken
> Out of interest, which is the correct terminology when defining a single point
> on a disk's surface - is it better to talk in terms of cylinders, or tracks?
I generally teach it this way. A track is the path traced by a single head
during a rotation of the spindle. A cylinder is the set of tracks traced
by all the heads for a single position of the arm. Thus specifying the
cylinder number specifies the position of the arm. Specifying the
head number selects the desired track from the set in the cylinder.
> cylinder/surface/sector or track/surface/sector. It's all just semantics, but
Track/surface is actually redundant since the combination of cylinder and
head uniquely identifies a track. In other words, the track number implies
the surface.
As to the usage in the floppy world, I'd guess that it started with the old
single-sided floppies. For them, a cylinder and a track were the same
thing. Then for double-sided floppies, people tended to talk in terms
of a track number on a side and didn't think in terms of cylinders at
all. But on multiplatter disks, the concept of a cylinder becomes a lot
more meaningful. Regardless of how many surfaces we have, it is
the difference between our current cylinder number and the desired
one that dominates the access time.
BLS
Yes that's it!!
All of their stuff was that bright red colour.
That reminds me...
If anybody hears of a Newbury Labs VDU (M2480) up for grabs or sale they
might let me know.
I worked there in the early 70's and another one of the guy's from those
days lives about
a mile from me.
rodsmallwood at btconnect.com
0118 971 4436
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of John Honniball
Sent: 21 December 2006 22:40
To: On-Topic Posts Only
Subject: Re: Bell 103 Datasets
Rod Smallwood wrote:
> Priot to that UK acoustic couplers where available. I remember
> connecting to a time sharing service (RSTS on an 11/70) using a
> ModTech coupler whilst working on VDU design circa 1973.
Was it by any chance this model Modular Technology modem:
http://www.flickr.com/photos/11328208 at N00/329472291/
(orange-red acoustic coupler, model XAC3001, full or half duplex, 300
baud).
--
John Honniball
coredump at gifford.co.uk
Hi
It was not mandatory to use BT modems but they were suppposed to be
approved with a (BATB) sticker on the bottom.
Both Hayes and USR produced UK versions. Plus there were some UK made
modems eg Modular Techology & Dowty.
Priot to that UK acoustic couplers where available. I remember
connecting to a time sharing service
(RSTS on an 11/70) using a ModTech coupler whilst working on VDU design
circa 1973.
Rod Smallwood
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: 20 December 2006 23:59
To: cctalk at classiccmp.org
Subject: Re: Bell 103 Datasets
> In the UK at that sort of time you were presumably required to have a
> GPO (later BT) modem and nothing else, but I'm afraid the web seems to
> be rather
I beleive so, since everything connected to the phone line had to be
rented from the GPO.
I can't help with dates, but I do have a few old ex-GPO modems in the
collection.
The Modem 2B is a large box (about 16" square and 7" high from memory.
It's 300 baud, original and answer. The front panel opens by undoing 2
captice screws at the bottom and then hinging it up (there's a little
'stay' to keep it open). Insider are 4 plug-in modules -- PSU,
Demodulator, Control, Modulator, with testpoints, fuses, and adjustments
on the front panels.
The modulator appears to be a VCO with switched control voltage. The
demodulator has 'tobacco tins' which cotnain complex LC filter networks,
and appears to work by mixingthe incoming signal with a lcoal
oscillator, extracting the 'sum' frequency, and feeding that to a
discrimiator circuit (similar to one of the standard ones used in FM
radio receivers, I forget which). It's all discrete transistors and
relays (in the control module), no ICs.
The Modem D1200A is similar in construction and design (and seems to be
the same case) but is 1200/75 baud (I forget which way round, it may
well be the 'host' end of a Prestel link).
The Modem 13A is somewhat later. It's a plinth that's screwed to the
bottom of a type 746 telephone (one of the standard desk telephones of
the 1970s). the phone has buttons to select voice or 'data' in front of
the handset rest. The circuitry seems to use several metal-can (10 or 12
lead TO5-like cans) ICs that I know nothing about, and alas the
schematic diagram inside the phone just shows the wiring to the extra
switches and to the modem unit, no details of the internal circuitry of
the modem itself. Again it seems to be 300 baud, probably originate
only.
-tony
Several months back, we talked about a calculator built from TTL. It came
>from a 1970's article in Practical Electronics, an English Magazine.
I had 7 requests for copies, which I mailed directly to the requestors.
Apparently they disappeared into a black hole, because I didn't receive a
single acknowledgement, let alone a thank you.
So for those still interested, Al Kossow scanned my copy and posted it on
bitsavers:
http://www.bitsavers.org/pdf/practicalElectronics/digi-cal/Digi-Cal_Jul72-Ma
y73.pdf
Billy
Mil-Spec in the US is exempt from lead-free. Bonding, whiskers (growing
shorts) and the like are know quantities in leaded; and lead-free
formulations are still evolving--and improving. A long term concern is what
happens to the leaded parts supply. Some of the manufacturers I've spoken
with say they will continue to produce lead parts for mil, areo and medical,
but will watch the market. No comment on what this will potentially do to
leaded parts prices. I have a small stock pile of leaded parts for one
application I support, mostly for price stability, and hopefully I will find
an appropriate electrical and mechanical bond system by the time I run out.
A nice side effect of RoHS, is that many companies are discounting their
lead parts. We picked up a nice stock of MicroChip [direct] parts from
.18-.40 cents on the dollar for example.
Chers,-jp
