[GreenKeys] Fwd: Why 1.42 ?

[Don Robert House]

Many thanks Ben!
Hope to see you when the weather gets better.
Don


-----Original Message-----
From: Don Robert House <drhouse at nadcomm.com>
To: Ben Stephens <K9kom at aol.com>
Sent: Tue, 28 Mar 2006 14:56:04 -0600
Subject: Fwd: Why 1.42 ?

Charles Ring wrote:
I remember printing 65 wpm (not 66) on a 15 with no problems and no  
adjustments; that is 60 wpm/45.45 baud with one stop bit rather than  
1.42. I have no doubt a 28 could do it even better. I'd consider two  
stop bits to be too much so I would use 1.5. I know the extra length  
for the stop bit is a "catch-up" safety margin but I have forgotten  
why it is 1.42 rather than 1.5 on the mechanical printers.

73 de W3NU

Ben,
Now I cannot remember.  Can you refresh my memory?
Thanks,
Don
=

Don,

I once heard the detailed reason for the 1.42 stop bit length, but  
that was decades ago and I have forgotton it.  However, it went back  
a long way to the very beginnings of printing telegraphy, with two  
different and potentially competitive firms competing on a reliable  
system of machine telegraphy.

The first group was out at Bell Labs in New Jersey, and they were  
working with some sort of a system where the transmitting and  
receiving shafts ran at the same speed.  With a 1.0 stop bit, the  
machine would transmit in a sort of synchronous manner as long at  
everything went well.

Out in Chicago, the Krum boys were working with a system where the  
receiving shaft went faster than the transmitting shaft, with the  
receiver actually coming to a complete stop briefly before starting  
again at the leading edge of the next start pulse.

Of course, the two systems were incompatible.  Bell Labs had the edge  
in being part of the American Telephone and Telegraph Company, with  
Western Electric and the Operating Companies as a captive market.   
Morkrum wanted to sell into this huge market, and the 1.42 stop bit  
was a compromise which enabled its products to work on a circuit with  
the Bell Labs equipment on the other end.  I don't recall the  
technical details which led to 1.42 as the compromise solution.

Anyway, the Morkrum system quickly proved itself superior, and the  
Bell Labs system was dropped and forgotton, but the 1.42 stop bit had  
established itself as a Bell System standard.  As we all know so  
well, a lot of current effort in common carrier communications is to  
retain smooth operation with the older legacy equipment.

73, Ben Stephens K9KOM
NNNN