[GreenKeys] (no subject)

[Jeffrey Golas]

Well that answered a longtime question I had lol. Thank Duncan!

Jeff

> On Dec 19, 2025, at 9:01 PM, Duncan Brown <duncanancy at earthlink.net> wrote:
> 
> 
>> On 12/19/2025 5:27 PM, Harold Hallikainen via GreenKeys wrote:
>> The tape reader is interesting. Instead of a distributor like the model 14
>> TD, it appears there is a cam that pushes up the hole sense pins one at a
>> time. I suspect there is a switch for each of the hole sense pins. If they
>> are open when the pin is down and close if the pin can go up (mark), and
>> the switches are in parallel, we get the parallel to serial conversion by
>> just sensing the holes one at a time. Again, clever!
>> 
>> Harold
>> https://w6iwi.org
> 
> Harold,
> 
> My first immersion into TTYs was in the US Army as a TTY repairman. I wondered why the Kleinschmidt tape readers were so simple compared with the old Teletype Corp. M14 tape readers with the big distributor.
> 
> It turns out, that from Emile Baudot's day (1880s) into the 1920s, all keyboard and tape readers operated with parallel output. The 5-bit parallel signal of multiple units was then sent to a distributor to produce a time division multiplexed signal.
> 
> When the Start-Stop method was started in the mid 1920s, they continued to use the old parallel tape readers, but now each tape reader needed its own distributor to convert it to serial, thus the name "Transmitter-Distributor."
> 
> The next generation of TTYs (Kleinschmidt Labs and Teletype Corp. M28)  in 1950 were all serial and simplified things with just one transmitter contact and they used cams to produce the proper timing.
> I assume that the European  M14 & M15s with tape readers did the same thing.
> 
> So the Kleinschmidt and M28 tape readers read the tape sequentially and generate the serial data signal directly, no need for the parallel-to-serial conversion of a "distributor".
> 
> (I don't know why they went back to a distributor in the M33)
> 
> Have fun,
> 
> Duncan
> K2OEQ
> 
> 
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