Date   : Thu, 22 Oct 2009 08:19:48 +0100
From   : pete@... (Pete Turnbull)
Subject: BBC Model B Issue 3 Circuit Diagram

On 21/10/2009 23:36, Ian Stocks wrote:
> Pete Turnbull wrote:

> Clock link 4 = 600K?

According to the schematic, 4 and 5 are the same -- but I expect you're 
right, for 600K would make more sense.

>> The terminator parts (it's a proper active terminator) are:
>>
>> R54 - 100K
>> R56 - 100R
>> R42 - 56R
>> R43 - 56R
>> D3 - 1N4148 (with the cathode connected to the junction of R56/C22/R42)
>> C19 - 10?F electrolytic
>> C22 - 10?F electrolytic
> 
> 
> Interesting, I presume this is just teminating the data side, Not enough 
> parts for both the data and clock.

Yes, it is.  I suppose if you add two more 56R resistors you could 
terminate the clock as well, but Acorn's original Econet terminators 
were only ever on the data lines.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York