Well, then why don't the other phones sound out the data string with the
ringers?
>Wrong.
>
>Caller id senses the ring and does not go off hook as that would
disturb
>the CO and it is uneeded. Instead the ring is an alert to the caller
ID
>that data will follow and it's already camped on the line using a
non-DC
>(capacitor coupled) connection to avoid loading the line. this allows
>it to hear the ring and the data.
>
>Allison
>
>
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
Hi all,
At 11:09 PM 7/16/98 +1000, Phil wrote:
>-----Original Message-----
>From: dave dameron <ddameron(a)earthlink.net>
>>Speaking of books,
>>has anyone seen the book "We Built our own Computers" by A.B. Bolt,
>>Cambridge Univ. Press, published about 1966. ^^
>
>Yes, I've got it here (bought as part of a $3 per bag haul from a charity
>book sale a month ago).
...
>I see a few other replies, so that it is not all that rare :(
>- but what exactly did you want to know for?
>
OK, Thanks,
One of my collection interests is for computer construction books and
articles. This book was mentioned in another article without any details.
If copies are floating around, I might find one yet.
-Dave
Has anyone built any of these? Does anyone have any extra copies?
>Indeed it is. 1966 IIRC
Are any still in publication or recently gone out of?
>I don't think I've come across these - can you provided titles, etc,
please
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Hello, all:
I thought that I'd share with you that I'm beginning my own classic
computing web site. I was fortunate enough to find a gentleman in Vancouver
who will sponsoring this effort. His particular interest is in PDP
equipment. Right now, he hosts a PDP8 document archive.
The first thing to be posted will be scans of the printsets that I
recently got. I'd also like to reproduce the hardware user manuals that I
own (which are on the order of 2 or 3 copy paper boxes worth).
I also intend to post the Altair scans that I've been holding, server
space allowing, of course.
I'll take some time, but when it's up, I'll solicit document donations.
More to come...
Rich Cini/WUGNET <nospam_rcini(a)msn.com>
- ClubWin! Charter Member
- MCP Windows 95/Windows Networking
- Preserver of "classic" computers
<<<< ========== reply separator ========== >>>>>
> When a phone is on-hook (hung-up) there is a 48V potential on the line.
> When the phone is ringing, there is 90v (nominal) AC on the line during
> the ring cycle to activate the ringer. When a phone is off-hook (you're
> talking) there is 12v on the line.
I think the 48V on hook and 12V off hook is historical - in the days of
long copper wires back to the exchange, it was all done from the 48V
battery - 12V was all that was left after voltage drop when the 30mA or
so (apparently the carbon microphone needs at least 23mA to work well)
had to go the several miles to your house and back. May still be like
that, come to think of it.
Those on shorter lines had higher resistance phones to compensate. In
the 1960s (? What date is the 706 anyway ?), many UK phones had the
"line drop compensator" on a plug-in module, presumably so you could
swap it for one with different resistors...
Philip.
< > When a phone is on-hook (hung-up) there is a 48V potential on the line.
< > When the phone is ringing, there is 90v (nominal) AC on the line during
< > the ring cycle to activate the ringer. When a phone is off-hook (you're
< > talking) there is 12v on the line.
the voltages are wildly approximate. It's current that does the work!
On hook is sensed by some current flowing and the threshhold is about
5-10ma may be more. Ring is ac coupled but the voltage is set so the
energy level of the ringer is met despite the loop (line) resistance.
the only one that was nominal was onhook of ~48v.
Allison
In Denver try Fistell's Electronics and Crump Electronics and in Boulder try
J.B. Saunders.
- Doug
> -----Original Message-----
> From: Uncle Roger [mailto:sinasohn@ricochet.net]
> Sent: Wednesday, July 15, 1998 7:53 PM
> To: Discussion re-collecting of classic computers
> Subject: Denver sources?
>
>
> My girlfriend and I are hoping to go on holiday at the
> beginning of August,
> and right now, it looks like Denver/Boulder will be our
> destination. So,
> does anyone know of any good thrift shops/swapmeets/etc. in the area?
> (And, off-topically, antique or teacher stores? Gotta keep
> the gf happy
> too! 8^) Thanks!
>
>
> --------------------------------------------------------------
> ------- O-
>
> Uncle Roger "There is pleasure pure in being mad
> roger(a)sinasohn.com that none but
> madmen know."
> Roger Louis Sinasohn & Associates
> San Francisco, California
http://www.sinasohn.com/
Hi Tony and all,
At 09:28 PM 7/15/98 +0100, you wrote:
>>
>> [We built out own...]
>>
>> Oooh! Scan! Scan!
>
>Well, it's all relay logic, and switches, but it's still fun.
>
>May I also recomend 'Practical Robot Circuits' from the Philips Technical
>Library series. It describes a robot dog built from DF92 etc valves, and
>includes schematics. The radio control book in the same series is
>interesting as well.
>
This must be 30 or so years old.
Can one still get these from Philips? I didn't find anything on Philip's site.
Has anyone built any of David Heiserman's robots? He's written several robot
construction books. Some with hardwired logic, some with microcomputers.
-Dave
Yesterday I acquired two boxes, each about the size of a UK telephone
directory, that were described as "AppleTalk to serial convertors".
Opening them up reveals a Mac 512 motherboard, a nice Farnell psu,
and a homebrew card in place of Apple's analog board. There are a
couple of other mods such as the programmer and reset
switches mounted on the front panel, small speaker mounted inside the
case, no internal floppy, keyboard extender.
The Mac board in box #1 appears to be completely standard. The
homebrew board contains 2 * SN74LS221N and 1 * 74LS256N with a lead
joining it to a composite connector. Does anybody have any idea what
the video output might be for? I understand that there were a number
of homebrew video mods of this type published in Mac magazines in the
mid 80's.
The Mac board in box #2 appears to be slightly non standard. At the
location F3 the original SN74F253N has been piggy backed with a
7F153PC (I think). There are also a few connections to the chip at
location F2 and to a factory solder pad on the motherboard. The
homebrew board looks similar to that in box #1 but is better made and
clearly hand labelled "composite video".
Which size floppy drive should these boards support? The ROM HI is
Apple # 342-022 and ROM LO is # 342-0221.
Any thoughts,
Phil
**************************************************************
Phil Beesley -- Computer Officer -- Distributed Systems Suppport
University of Leicester
Tel (0)116 252-2231
E-Mail pb14(a)le.ac.uk
Spotted this in the DEC newsgroup. For our euro friends.
DO NOT REPLY TO ME - REPLY TO ORIGINAL POSTER
From: Peter Mueri <MPe(a)pop.agri.ch>
Newsgroups: comp.sys.dec.micro
Subject: FS DEC material
Date: Mon, 13 Jul 1998 20:14:18 +0000
Organization: 64 Bit Linux/AXP forever!
For Sale
1 Vaxmate Computer with HD Box sFr. 100
1 DEC uVAX 2000 sFr. 200
1 DEC uVAX 2000 4MB Memory Board sFr. 20
1 DEC VaxStation2000 RD54 RGB-19" sFr. 400
1 DEC Monitor 19" B/W VR100 55kHz sFr. 30
1 PDP-11/70 Plessey Core Memory sFr. 10
1 Rainbow Computer with DOS and CP/M and table sFr. 100
1 DEC VT100 sFr. 20
1 DEC VT240 Console sFr. 20
various DEC MFM HDs
Prices are pick/up prices in Switzerland.
Willing to trade-in McIntosh CPUs.
Peter
lwalker(a)interlog.com
