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

[Brooke Clarke]

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
-- 
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