Relay computers

[John Lawson]

On Sun, 26 Sep 2004, Gordon JC Pearce wrote:

> Tony Duell wrote:
>>> And slugged relays, with a big metal ring in the coil.  These either delay 
>>> opening or closing, but I can't remember which way round it works. 
>> 
>> 
>> I believe (without running upstairs to look in 'Telephony' [1]) that you 
>> can arrange for either a slow make or a slow release
>
> Yes, but I can't remember which end you put the slug at for which action
>

   Normally I'd research this and have the detailed info before responding, 
*especially* since I just recommended a lot of books on the Subject - but 
after a cursory Google and skimmming thru the texts that are near to hand, 
I can't find the actual detailed descriptions of the various 
electromechanical 'delay' schemes.

   From (faded) memory: If a copper ring is placed over the relay solenoid 
near the end, it acts as a transformer, and when the current is removed, 
it sets up a 'flux resonance' of sorts, acting to keep the magnetic field 
alive - this action decays over a period determined by the various 
parameters and physical layout of the relay - so the device delays it's 
drop-out for X milliseconds after the excitation voltage drops.

  NOW: I seem to recall that which 'end' of the coil (base or springs) has 
an effect, and I *think* that the opposite effect - delayed pull-in - can 
be gotten by using a soft iron ring in place of copper - the iron 
magnetization current is different from the copper coil windings and thus 
absorbs energy during the application of excitation current.

   Like Tony, I have the Bell System Technical Journal, Vol. 1, No. 1 
(1922) thru Vol 47 (1968)...  BUT I haven't the time/space/energy right 
now to go plowing thru all that just to look this up...   maybe this 
evening , *if* the project I'm working on is successful....


  Cheers

John






>> [1] A great 2-volume set on the UK telephone system, mine is the 1933 
>> edition IIRC. They contain _complete_ schematics for telephone exchanges 
>> (Well, OK, the circuit for each line is drawn once, not <n> times, but you 
>> know what I mean). They were the books that finally let me understand how 
>> telephgone exchanges work, and proved to me the dangers of giving a 
>> simplified explanation (in that I'd read plenty of simplified books on how 
>> telephone systems work and couldn't make any sense of them).
>
> Now, somewhere I have a very old book on telephony and telegraphy that sounds 
> very similar to that.  At least, I hope I still have - after my father went 
> silent-key around 10 years ago, it seems that a few people had some novel 
> ideas about what belonged to them (his Bob Dylan lp collection is long gone, 
> for one thing).  It had diagrams of the various sections of the exchange, 
> slightly simplified, and then another diagram detailing how they go together 
> (line finders, call routing, stuff like that).
>
> Gordon.
>
>