On Sun, 22 Mar 1998, Doug Spence wrote:
> > It sounds like a board from a telephone switch. (Especially the "125B"
> > label and the Western Electric chips.). I'd guess from 1985, based on
> > what I assume are the date codes.
>
> Interesting. I wonder how it ended up in a box of ISA cards (and one
> S-100 bussboard)? :)
>
> Please forgive my ignorance (and the potential off-topic repurcussions),
> but could this board's function be what it appears to be? (i.e. RAM) And
> if so, what use is that in a telephone switch? And could the switch be
> used to do any computing? ;)
Phone systems are, in effect, special purpose computers. They have a
processor, programming, and RAM to store the database during run-time. The
database will have the details of the phone system, such as the extension
number of each phone, the class-of-service for each phone, etc. The phone
systems I'm most familiar with (Siemens Saturn) have anywhere from half a
meg to 1meg of memory to store the database. A lot of times, the database
is loaded off of floppies (Saturns use 8" and 5.25" floppies, others use
3.5" drives and even hard disks).
I have an AT&T Horizon phone system (circa late 70s) which is significant
in the history of telephone systems as it was the first "key" system. It
uses an Intel 8008 processor. The switch I've been working with for a
while now (Cortelco Millenium) is based on an Intel 80286 and uses static
RAM to store its programming. Some interface cards, such as the T1/E1
interface, have their own 8088 processors to off-load the protocol
processing from the main system processor. So its in effect sort of a
parallel processing computer.
You can ask me more specific questions in e-mail if you'd like more
information.
Sam Alternate e-mail: dastar_at_siconic.com
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Received on Sun Mar 22 1998 - 04:46:28 GMT