and various output devices (such as the incremental magnetic tape recorder, 
typewriter, teletype page printer, etc. ). The reversible counters (one of which 
is required for each axis of measurement) are available in five-, six-, or seven- 
digit count ranges--all are fully bi-directional and direction sensing. The Coradi, 
Coradomat Series 21 is a sophisticated automatic drawing system with a relatively 
large work area. The internal memory capacity can be programmed for linear, 
circular, quadratic, and cubic interpolation. Further, it has an automatic line 
follower readout capacity; an absolute measure control but with incremental in 
put or output capability; an automatic subroutine capability on command; and a 
perforated tape, magnetic tape, card, on-line read-in and read-out capability. 
Drawing is accomplished by using light beams that are guided automatically over 
the surface of a film or photoplate. The Series 21 has a 200 station light photo 
printing capability. 
GERBER SCIENTIFIC INSTRUMENT COMPANY. 
The Gerber Scientific Instrument Company, Hartford, Connecticut, USA, 
has designed several control systems, graphic display systems, automatic digiti 
zers and line followers with stored programs. The most sophisticated of their 
equipment are the Series 2000 Control, the Graphic Display Table, Model 32, and 
the Gerber Automatic Digitizer. The Control unit is used to control the drawing 
table, to accept directly the computer language, to perform conversions, and to 
generate table instructions. It is a stored program control (rather than wired-in) 
with a relatively high core memory, parallel, single address with indexing and 
indirect addressing capabilities. Memory expansion is possible in order to in 
crease the computer capacity, if desired. The Control unit is capable of con 
trolling the graphical display tables in connection with complex parabolic and 
hyperbolic geometric pattern displays, high-speed contouring and curve fitting, 
in addition to performing general purpose computer tasks. The Model 32 Table 
is designed to operate at various speeds; relatively high speeds are possible 
but with proportionately decreased accuracy and repeatability values. A larger 
active working surface is provided. The Automatic Digitizer consists of a Line 
Follower, an Operators Console and a Digitizing Program. The line follower 
uses a vidicon sensing system. The operators console has a control panel, a 
foot^activated speed control,and a TV monitor--the latter allows the operator to 
view continuously the graphics being digitized. Control panel elements include 
mode switches, manual steering controls, status indicating lights, and X-Y axis 
position displays. The automatic digitizing program feeds into the computer 
memory all routines necessary to achieve manual and automatic digitizing; it 
interrogates the table encoders and compares data received with the previous 
data relative to line lengths, area, angle and slope; it provides a capability to 
the operator to return rapidly to the last valid data point in case of operational 
necessity; and it produces tape that may be used directly to machine the shape 
of the digitized graphics in the final material. 
MISCELLANEOUS. 
Several instruments and techniques have been introduced for the purpose 
of stereocompilation as well as for extracting high -resolution, digital map data 
directly from stereomodels and from existing map sheets. These are described