[GreenKeys] STUNTRONIC Parity Detector

[Don Robert House K9TTY]

We used one in our Data Test Center as an add-on to several data sets. A couple of the TTY shops used the parity detector with a stand-alone CX Reader.

The Type 4 Sender and Receiver used both vertical and cyclic parity errors in addition to check words added to the data stream.
They were amazing to watch sending and receiving at 2000 wpm.  The line interrupts caused the sender to stop and back up the paper tape.
The receiver would back up the tape through the punch and over punch rubouts (all 8 levels) then send reverse channel back to the sender to continue.
I was responsible for maintenance of one of the senders.  It worked pretty well, but the folks at the other end in Chicago had fits keeping the receivers running.
That was 1969 and the maintenance kits for the Type 4 were $2,500. each.

Memories,
Don
K9TTY


On 08 Aug 2015, at 8:12 PM, Jim Haynes wrote:

> 
> I know some of the history behind this.  Working on Dataspeed Type 2 about
> 1963 we realized it would be trivially easy to add a parity check to the
> transmitted data, since the bits of a character were being shifted through
> a register and we would only need to add a flipflop that would change
> state on each mark bit.  So we hacked up the system in the lab to add
> this feature.  We started out calling it "error detection" and soon learned that would not fly because (1) the System did not want the customers to imagine that errors were possible, and (2) it only detected
> some of the possible errors, and (3) how would it be used operationally?
> 
> If there was a transmission going on with operators watching then they
> could interrupt it and start over.  But if the transmitter was unattended
> and being called up at night what should be done?  Denounce the whole
> transmission and repeat it the next day?  Or accept it and try to make
> the best of it?
> 
> Eventually the name problem was solved by calling it "vertical parity
> check" which is exactly what it was.  But I don't know if the feature
> was ever offered in the production equipment.
> 
> 
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