3. Electronics Equipment 
Outside of the immediate operating area there are four racks of 
electronic equipment associated with the drive, metering, readout and 
programming requirements of the two measuring tables. 
System Operation 
1l. Previewer 
At the previewing station, the operator clamps the plate upon a 
rotary plate support with the fiducial marks (or any two images) roughly 
aligned with the axes of motion of the measuring table. During successive 
observations of the positions of the two points within the field of view of 
his microscope, he uses a vernier control to make half-adjustments of the 
plate support, until the two points track within acceptable accuracy. All 
translations are controlled by the operator's command inputs to the veloci- 
ty-servo drive system. 
The operator then translates the plate until the point desired as 
the zero of the coordinate system is centered in the field of view. Upon 
his command to the programmer the bi-directional coordinate counters 
are set to zero. All subsequent translations are monitored cumulatively 
by the coordinate metering system and the bidirectional counters. The 
condition of the counters is continuously displayed in the visual readout. 
Before or after locating an image the operator can insert con- 
stants relating to the image into the system via a ten-decade keyboard. 
The constants will remain in effect until cancelled by the operator. 
When the operator gives a readout command to the programmer 
this circuit functions, along with the distributor which it controls, to pro- 
duce a data output record in a format governed by the patching of the pro- 
grammer plugboard. This output record consists of the keyboard con- 
stants and coordinate measurements, punched into an IBM card and printed 
on paper. 
The previewer is capable of accepting prepunched image cards, 
which do not require insertion of keyboard data. For these cases the op- 
erator sets the control panel so that the programmer causes the card 
punch to skip over the constants fields. 
The programmer, upon preset commands by the operator, can 
insert special punchings into the IBM card, in specified columns, to modi- 
fy the subsequent behavior of the Automatic High Accuracy Comparator, 
These modifications permit manual centering of the image, and allow for 
substitution of new constants in the comparator.