shades,
Here is another! The first #1 EAX (Automatic Electric) was installed in St. Petersburg, FL beginning in Nov '71 (if my memory serves correctly). There was a 'marker' routine that had 300+ 'steps' (software) in the routine. Anyway, about step 136 or so, the marker did a FPC (foreign potential check) on the line calling for service, prior to connecting a 'reciever' (collects digits). If a foreign potential was detected, than the 'marker' would enter a 'fail' state, and go 'off line' to test itself and insure that the FPC was working correctly. The 'mate' marker would then begin to process the call. So far so good, so you would think! After the system was installed, someone came up with the idea of plugging the 'phone line' into 110vac! Well, now let's see! That 1/2ohm short (resistance of ac line) looks like 'off hook' to the switch. We step along to step 136 (about 100ms it think) and oh-oh, foreign potential detected (remember that 110vac?), off line to 'self test' (takes several seconds mind you!) and on comes the 'mate' marker! You guessed it, step 136, FPC fail, 'off line' test, oops - no markers, no dial tone, can you say 'OUTAGE'! Pretty clever, no? Had to 'crank' a couple of hours into that one! Fun,fun,fun! ( We did get it fixed though, I think we disabled the FPC, if memory serves, of course that defeated the ability of keeping 'high voltage' from entering the switch, and in the 'Lightening Capital of the World', that is not a particurlarly good idea!
How's that one?
Ken |
