[VoIP] Spotted On Ebay

Thu Feb 7 03:13:40 CST 2008

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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>> VoIP at ckts.info
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>
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