[GreenKeys] 28ASR Selector Magnet Driver and "Blinding"

[Robert Goff]

Many thanks to John (DDD) and Nick for the good info on the sync pulse
magnet.  Whudda thunk it would be such an easy fix! And a special
thanks to Nick again for the great resource of his website!

Having the sync pulse problem licked the next challenge has been the
177010 Selector Magnet Driver installed in the LESU of this 28ASR.  It
seems like it is stuck in the marking position all the time, leading
me to believe it either a) is broken or b) is blinded.

The manual for the selector magnet driver gives instructions for
blinding both when the signals need to be monitored and when they
don't.

The example for the first instance is : "the stunt box of a Page
Printer (which would be receiving the line signals through its own
selector) could be arranged so that its contacts would blind the
Driver of a Reperforator at the receipt of a certain character
sequence, and would unblind it at the receipt of another sequence."
---that part I understand. In this case a jumper in the PS is removed
and the terminals run out to relay contacts on the stunt box.

With unmonitored signals the PS is simply jumpered to put the
transistor in a steady marking state.

Question is: why would a person ever want to do this? There doesn't
seem to be any way to switch in and out of blinding. Is there a way to
see if a selector has been blinded without pulling the whole LESU out
of the cabinet?
Anybody run into this?
Robert
W7MKA