[VoIP] Spotted On Ebay

Thu Feb 7 06:22:23 CST 2008

No book is worth that amount of money to me! I thought £30+ for a 1928 
book about London Underground and £40+ for an IRSE  reference work on 
British Railway Signalling were close to my limits when i bought them on 
Ebay. Interestingly I saw someone asking a ridiculous starting price of 
£50+ for volumes 1&2 of Atkinson's Telephony recently and they were late 
editions.

Brian

Ian Jolly wrote:
> 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
>>>> _______________________________________________
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>>>> Project Web Page: http://www.ckts.info/
>>>>         
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>
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