In all cases the computer program is the key 
to the use of the instrument. The computer may 
by considered a general purpose machine to the 
extent that the desired functions fall within its 
storage and arithmetic capacities, which I will 
discuss later on. Programs which have been 
previously written, coded, and prepared on 
punched paper tape are loaded through the tape 
reader on the Flexowriter. In this way a change 
from one mode of operation to another may be 
achieved with convenience and minimum down time. 
DESCRIPTION OF EQUIPMENT 
Fig. 2 shows the main computer-plotter console 
with the plotter cover in the raised position. 
Thisunit is 51 inches long, 46 inches wide, and 
44 inches high. It weighs approximately 1600 
pounds, The X-Y plotter was built by Electronic 
Associates, Inc., to our specifications and, for 
installation, is separable from the base cabinet 
containing the digital computer and input-output 
units. The base cabinet is modular and can be 
further subdivided to facilitate installation or 
removal of the equipment, The master control 
panel shown governs operational mode selection, 
insertion of operational constants germane to the 
task being performed, and various other control 
functions affecting the computer and plotter. 
One of the operational constants mentioned would 
be,in a typical case, the geographical coordi- 
nates of the navigational control stations, 
Another would be the chart scale factor, etc. 
Fig. 3 shows the Friden Flexowriter used with 
the instrument. Ina typical case the machine 
prints out positional and other parametric data 
required by the program and simultaneously 
punches the same data on coded paper tape. The 
punched tape data may be used for further data 
processing at a central facility as well as for 
recreating the plotted data on the same or 
similar instrument at another time. 
INPUT ANALOG-TO-DIGITAL CONVERTERS 
As mentioned previously, data enters the 
console as analog voltages which are converted 
internally to binary form. 400 cps.synchros 
have been standardized on for transmission of 
shaft positional data to the console. A bank 
of several shaft position-to-digital converters 
is provided to accept this information and con- 
vert it into 10-bit binary numbers, Relays are 
used to switch the limited number of converters 
among the many data sources necessitated by the 
various operating modes, thus attaining a 
measure of input flexibility while maintaining 
economy of equipment. 
Fig. 4 is a schematic diagram of one analog- 
to-digital converter presently used. It is a 
simple servo follower in which the voltage from 
the 400 cps. synchro transmitter at the data 
67 
source feeds the stator of the control trans- 
former in the converter unit. The amplitude of 
the voltage across the rotor will be proportional 
to its angular displacement from the null 
position and the phase of the voltage will 
indicate the direction of the displacement. 
error voltage is amplified by the transistor 
servo amplifier,which then drives a servo motor 
coupled through a gear train to a 10-bit code 
wheel and to the control transformer rotor. 
With the servo nulled, the digital number 
generated by the code wheel corresponds to the 
angular position of the remote synchro trans- 
mitter. A photograph of one of the servo 
follower units is shown in Fig. 5. These units 
are manufactured by the Datex Corporation. 
The 
Other means of data entry can be provided in 
those cases where digital data are already 
available or where voltage-to-digital conversion 
is required. 
DIGITAL COMPUTER 
The digital computer contained in this 
instrument is a general purpose transistor 
computer designed for shipboard applications. 
The program is stored in a magnetic drum memory. 
Physically, the computer is subdivided into 
printed card chassis, as shown in Fig. 6, which 
are mounted on the cabinet doors and hinged on 
one side to provide access to the chassis 
wiring at the back, Each chassis contains 
approximately one hundred printed solid-state 
logic cards of standard Westinghouse design. 
They contain accessible test points for trouble 
shooting and are easily removed and replaced. 
The computer contains five such chassis, 
including input-output units, in addition to 
other subassemblies containing power supplies 
and memory circuits in the interior of the 
cabinet. 
Although the design of the computer is an 
interesting subject in itself, a detailed 
discussion of it would not be appropriate or 
possible here, Needless to say, it is, in terms 
of physical and technological complexity, the 
principal item in the instrument. The philosophy 
of its design was founded on the requirement 
for a computing facility combining rapid 
arithmetic computation in real time, precision, 
reasonable storage capacity, and physical com- 
pactness. A summary of the important computer 
characteristics should be of interest and will 
be listed. 
Summary of Computer Characteristics 
Input-Output Unit: 
Up to 32 programmed inputs of 23 bits each 
(parallel transfer) 
Up to 512 outputs of 23 bits each (parallel 
transfer) 
