[GreenKeys] Western Union Ticker-5A Stock Quotation Machine

[Bob Camp]

Hi

One simple way to drive a pure polar coil is to put it between a  
bridged stereo amp chip's two outputs. An appropriate resistor in  
series will allow you to set the current to a reasonable level.

The high voltage supplies normally used allow you to get a highly  
inductive coil "up to current" fast. Regardless of weather you use a  
constant current loop or a resistor based loop you need a reasonable  
amount of voltage to get the current moving fast.

Typical constant current loop voltages run up around 60 to 90 volts.  
Resistor based loops run from about 120 volts up to (rarely) 250 volts.

If you want to go nuts you can build a switcher along with a data  
delay and only have the voltage on the loop coil when you need it.

Bob
KB8TQ


On Apr 17, 2007, at 6:33 PM, Brooke Clarke wrote:

> Hi:
>
> I'm trying to bring a Western Union Ticker-5A Stock Quotation  
> Machine back to life.  This is the machine that replaced the older  
> stock ticker machines that were under glass domes to keep down the  
> noise.  I'd say that it's father was the Edison Universal stock  
> ticker that changed Edison from someone who was broke to a multi  
> millionaire.  It's mother was the model 26 Teletype machine since  
> they both use a similar, but not interchangeable, selector cage.
>
> It's my understanding that the 26 was good for 100 CPM yet the 5A  
> was good for 500 CPM.
>
> The 5A uses a permutation code that consists of 5 bits but instead  
> of using a character for shift to numbers and another character for  
> shift to letters the 5A uses another code bit for this so the total  
> number of bits in the code is 6.  This solves the stuck in figures  
> problem.
>
> But unlike teletype machines the 5A does NOT use start and stop  
> bits.  This is one of the things that makes it fast.
>
> The thing I'm working on now is how to drive it.  The input goes to  
> a polar relay that expects to see current polarity reversals, not  
> the on off keying that a normal teletype machine uses.  Testing has  
> revealed that it wants to see 50 to 100 ma and being a 20 ohm coil  
> a little over 1 volt is all that's required.
>
> Are that circuits already in existence that will take in RS-232 and  
> supply the bi polar drive current?  I think that might be more  
> common in the UK or Australia than in the US.
>
> Why do teletype machines typically have loop voltages in the 100 to  
> 200 volt area?  Could these be replaced by current sources that  
> have a voltage compliance a litter higher than the voltage drop  
> across the input relay coil?
>
> For more on the 5A see my web page:
>
> http://www.pacificsites.com/~brooke/WU5A.shtml
>
> Have Fun,
>
> Brooke Clarke, N6GCE
> -- 
> w/Java http://www.PRC68.com
> w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
> http://www.precisionclock.com
>
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