[tnmoc] Tricky Switches

I’m trying to workout the exact coding needed for CB RESP on the test device. Now my memory is I was told all the carriage events listed in the circuit diagram fragment below are signaled. However, that doesn’t sit well with the wiring for them being in series.

1053 Carriage Switches

An email discussion with Olly last night dug out the fact that the IBM circuit diagrams use their own standard for symbols not  the common one.  So what exactly do those little circles on the top and bottom switches mean?  The upshot is that it looks like I’m going to have to get out the meter and hand cycle tool to work out what actually happens with the coding of those switches.

3 thoughts on “[tnmoc] Tricky Switches”

  1. Peter should be pointing me at an explanatory document on IBM diagram symbols which might help. TBA
    Note 4 on ZW101 implies that this section might be optional? Do you know what “OLSA” is?

    1. My copy of ZW101 has the dotted box Note 4 is talking about not covering CB7, CB5, & CB2 which are the bits I’m interested in.

      Guessing a bit more, the CBx probably means circuit breaker x. CB RESP is active low, and the other end is wired to the +48V line. So yes it probably does signal all those events by breaking the circuit when they occur. Any one of them breaking will send the line low. I did say I know nothing of electronics didn’t I? 🙂

      OLSA is probably best decoded as Obscure Legend for Service Aid. As in an IBM only initialism for a test tool or program then in the Customer Engineers’ service kit. It could well have been something as commonplace as an oscilloscope. IBM would never be so direct as to use the ordinary name when they could use something obscure.

      Next step is to hunt in the docs for the RPM of the motor / cycle shaft / op shaft so I can work out the pulse width of the signals. Looks like I am going to need that timer interrupt you talked about after all.

      1. We still need to know what the circles are. In the same way that the signalling every event memory started I have the apparently random idea that the circles mean rocker switch like action. It’s possible the timings for CB2 and CB7 pulses could be plus one rotation to allow for the mechanism to be reset to home state on a second revolution. If I’ve guessed how a cam activated rocker switch would work correctly?

        When you get random unadorned facts arriving in your memory that much later prove to be from one long forgotten casual conversation about something you were not involved with ever it is best to check when it happens again to see if your memory is being peculiarly reliable.

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