[VoIP] Spotted On EBay

Thu Feb 7 06:27:26 CST 2008

Ian,

The book costs $1500 US!  Does a working Strowger exchange switch come with
it?  

Lee

-----Original Message-----
From: voip-bounces at ckts.info [mailto:voip-bounces at ckts.info] On Behalf Of
Ian Jolly
Sent: Thursday, February 07, 2008 4:22 AM
To: Ian Jolly; Voice Over IP Tandem for Analog Switches
Subject: Re: [VoIP] Spotted On Ebay

Forgot to mention - there's a good book on Strowger systems at 
http://tinyurl.com/2wbfzt     I've got my copy!  It is of use to me as I 
have couple of final selectors (connectors) from the UK's first public auto 
exchange which the book describes in detail together with all its large pull

out circuit diagrams.  When I get time I hope to build a small demo switch 
incorporating the selectors/s.

I think this book is about the same date as the one Mark is using !

Ian J

----- Original Message ----- 
From: "Ian Jolly" <ian at uax.org.uk>
To: "Voice Over IP Tandem for Analog Switches" <voip at ckts.info>
Sent: Thursday, February 07, 2008 9:13 AM
Subject: Re: [VoIP] Spotted On Ebay

> I've replied at length to Mark on this one to save clogging the list up 
> with
> 'non-CNET' info. Also pointed him in the direction of  the bible as used 
> for
> UK systems - Atkinson's 'Telephony' and its predecessor - by Herbert &
> Procter which covers most UK manufactured systems.
>
> Ian Jolly
>
>
> ----- Original Message ----- 
> From: "Mad Mark" <madmanmarkau at hotmail.com>
> To: "Voice Over IP Tandem for Analog Switches" <voip at ckts.info>
> Sent: Thursday, February 07, 2008 3:01 AM
> Subject: Re: [VoIP] Spotted On Ebay
>
>
>>
>> I won the items, and they should be arriving in a few days, if all goes
>> well. Sounds like that S17 is the perfect novelty piece for a display. 
>> Now
>> I understand why someone said it was rather unusual.
>>
>> Anyway, I'm going to copy/paste an E-Mail I sent to Ian and John. Perhaps
>> you can help me too.
>>
>> *** Begin message ***
>>
>>
>> I've been reading up on EM
>> switching gear from the Automatic Telephony book by Arthur Bessey Smith
>> and
>> Wilson Lee Campbell, and have a couple of questions about the line and
>> cut-off
>> relays when using a line finder.
>>
>>
>>
>> First, can you confirm my
>> understanding of this. When the customer goes off-hook, the Line-Relay
>> (LR)
>> actuates, connecting the motor-magnet (MM) of the line-finder to the
>> private
>> wiper (PW) and off into the rest of the exchange. If the PW is grounded 
>> by
>> the
>> rest of the exchange, the current flows via the MM through the PW and to
>> ground
>> via the rest of the exchange, advancing the line-finder (because the MM 
>> is
>> basically a chopper circuit).
>>
>>
>>
>> When the wipers rest on an idle
>> trunk, the PW is no longer grounded, so the MM doesn't have a ground
>> connection
>> for power so can't actuate. However, the cut-off relay (COR) has enough
>> current
>> via the MM to actuate, cutting the customer loop through to the idle
>> trunk, and
>> connecting the PW to ground via the LR, busying the trunk circuit. 
>> Because
>> the
>> COR has now actuated, the LR is cut off and slowly releases, being a slow
>> release relay.
>>
>>
>>
>> Here's the part I don't quite
>> understand. After the LR has released, it disconnects the ground from the
>> COR
>> relay. What is now supplying the ground connection to keep the COR
>> actuated? Is
>> it something at the other end of the trunk? Or am I missing something?
>>
>>
>>
>> The following are assumptions
>> based on the circuit diagram I have. When the called party disconnects,
>> the
>> ground is removed from the Trunk Release line and PW, thus removing 
>> ground
>> from
>> the COR, returning the relay to the normal state and connecting the
>> customer
>> line back onto the LR. The LR is getting power because the customers
>> handset is
>> still off-hook, so it actuates again, and causes the COR to actuate,
>> reconnecting the line to the trunk, and cutting power to the LR. The LR
>> releases AGAIN, causing the COR to release, etc. One huge chopper circuit
>> is
>> happening. Or, maybe the trunk circuit sees the momentary ground on the 
>> PW
>> and
>> applies its ground to the PW as if the customer had just picked up their
>> handset again. I am most probably misunderstanding this greatly, as I
don't
>> see
>> this happening as being a good thing.
>>
>>
>>
>> And I am assuming the connector
>> switch or some circuit further up the trunk handles all call disconnects.
>>
>>
>>
>> Also I'm assuming the line-finder
>> rotates only in one direction and has two sets of wipers, one set coming
>> into
>> use at position 0 when the other set (positioned at 180 degrees) leaves
>> position 24 (or whatever the maximum is) and rotates into dead air. Is
>> this correct?
>>
>>
>>
>> Can you give any clarification on
>> these points?
>>
>>> Date: Mon, 4 Feb 2008 16:31:39 -0500
>>> From: martin at Princeton.EDU
>>> To: voip at ckts.info
>>> Subject: Re: [VoIP] Spotted On Ebay
>>>
>>> Mad Mark wrote:
>>> > Someone on the CNET-UK-I mailing list spotted these items on E-Bay:
>>> >
>>> >
>>> > 130193124276
>>> >
>>> > 130193124377
>>> >
>>> > 130193124440
>>>
>>> The first appears to be a standard BPO type 1 uniselector.  The third is
>>> a BPO "miniature' uniselector (type 4 if memory serves.)
>>>
>>> The second item is rather interesting.  I *think* it's a Siemens
>>> digit/pulse counting switch, developed by them for their number 17
>>> system (the one that used motor uniselectors.)  Unfortunately, from the
>>> pictures it appears to be missing it's wipers, so it's no ore than a
>>> display piece.
>>>
>>> S17 was never used in public service in the UK as far as I am aware, but
>>> maybe it was in Oz...  One of the big oil companies, I forget which, had
>>> a big S17 PBX installation in their London office.
>>>
>>> Martin
>>> _______________________________________________
>>> VoIP mailing list
>>> VoIP at ckts.info
>>> http://lists.ckts.info/mailman/listinfo/voip
>>> Project Web Page: http://www.ckts.info/
>>
>> _________________________________________________________________
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