[GreenKeys] old computers 'n stuff

[Jim Walls]

OK, here is my old computers and Teletype story.
  
 When I started working on the Testboard for a major electric utility, we 
had an old alarm system that monitored alarms (power, generator, door, 
temperature, microwave, and mux systems, etc) at all of our remote 
communications sites (almost 100 locations).  The system was based on a PDP 
1104 computer.  The computer had a current loop that had a Model 35 ASR TTY 
as a permanent logger and a TI Silent-700 that we could tear off, make 
notes, etc.  The TTY was also used if we needed to load the configuration 
or executable code using the paper tape reader.  In the event of a cold 
boot, we would open a book that gave the first about 20 bytes to load using 
switches on the front panel.  Then you would enter an address and press the 
"Run" switch.  That would execute the bootstrap that has been manually 
entered, and it would load the executable and configuration from the paper 
tape.  For a warm boot, we did not need to load the bootstrap, just give 
the address to run.  The same book that had the bootstrap data also had the 
entire executable code that could be loaded manually from the front panel 
switches.  Not something that we EVERY would want to do as it was many 
pages of data.  The maintenance of the computer was handled by our Power 
Systems Control people who ran the computer system that managed the entire 
power system.  They knew the computer, but not the TTY. 
  
 So one day I came in at the beginning of my shift at 1400 and I find one 
of the PSC guys loading a paper tape into the TTY.  There is a small pile 
of shredded tapes laying on the floor.  so I ask the guy what's up.  He 
said he was having to reload the alarm computer.  Then he comments "I sure 
hope this one works, this is the last tape".  As he's about to hit RUN, I 
yelled at him: STOP!  After I was assured that he was not going to hit run, 
I walked into the Testboard and grabbed the Wire Chief and showed him what 
was going on.  I then asked him if he wanted me to take that last tape and 
take it home and copy it on my known working M35 ASR.  He immediately said 
GO and then told the PSC guy to find someone who could get the TTY to not 
shred the tape.  So I go home and first test my tape reader by playing a 
picture tape I had.  Then I copied the first couple seconds of that picture 
tape and compared the original to the copy (very easy since it was a full 
punch chad type tape punch).  Once I was satisfied that my equipment was 
working properly, I made several copies of the original tape and brought 
them back to work.  By this time, the PSC people had found their one guy 
that could do at least some maintenance on the M35 and gotten it to work 
properly.  Loaded one of the tape copies and ran the bootstrap and this 
time it worked properly. 
  
 A few weeks later, the M35 was sent out to a professional for a complete 
going over.  Mainly all it needed was a good cleaning.  Turns out that the 
sprocket feed paper we were using would often not have the sprocket holes 
fully punched and running through the M35 would generally result in the 
little round disk of paper that was the sprocket hole getting dislodged and 
dropping into the printer basket.  After it was returned, I was directed to 
clean the printer every month on the Sunday afternoon that I was working 
swing shift.  First time I did that, I typed a comment that the Teletype 
was going off line for cleaning and timestamped it.  When I was completed, 
I timestamped it and wrote the following comment:  "Teletype back in 
service after removal of approx 1,000 LRPDs".  Monday afternoon, I get a 
phone call from the engineer that reviewed the daily alarm log, who asked 
me, "What the heck is a LRPD?"  I said "Little Round Paper Disk".  The M35 
never gave any trouble from then until that system was retired a few years 
later.
  
 73 ---
 Jim Walls - K6CCC
 jim at k6ccc.org