Fig. 1a.  The perforator control cycle begins at bottom dead center (BDC), when the punches are
completely inserted through the paper into the die.  As the shutter edge enters the photointerrupter,
a trigger signal to the PD1 controller is generated as the light beam is shut off.  The photointerrupter
stops conducting, equivalent to opening a mechanical switch.

1.  PD1 mode = trigger:parallel -- nothing happens

2.  PD1 mode = trigger:separate -- The PD1 controller and PUNCH program issues commands
to shut off current to the solenoids which are to turned off at this row.

The crankshaft continues to rotate through 45 and 90 degree positions as the active punch pins are
pulled from the die.
 
 

Fig 1b.  Somewhere around 135 degrees the punch pins have been lifted clear of the paper and the
motor may be commanded to advance the paper.  As depicted in the illustration, at 135 degrees the
shutter edge leaves  the photointerrupter, and a trigger signal to the PD1 controller is generated as the
light beam comes on.  The photointerrupter now conducts, equivalent to closing a mechanical switch.

1.  PD1 mode = trigger:parallel -- The PD1 controller and PUNCH program issues commands to
(a) advance the paper, and (b) turn on current to the solenoids which are to turned on at this row, and
(c) to shut off current to the solenoids which are to turned off at this row.

2.  PD1 mode = trigger:separate --  The PD1 controller and PUNCH program issues commands to
(a) advance the paper, and (b) turn on current to the solenoids which are to turned on at this row.

The crankshaft continues to rotate through top dead center (TDC) at 180 degrees while the paper is
advancing and the solenoids are moving the interposers.
 
 

Fig. 1c.  Somewhere between 225 degress and 270 degrees the active punch pins contact the paper
and begin punching through the die.  The crankshaft continues to rotate until the shutter interrupts
the light beam at 0 degrees (BDC) and the control cycle repeats.