Display panel permits information entry and erasure using a probe, and has an inherent storage capability for use on time-shared systems. Data input need not be online. Other advantages include direct display of input and output, simplicity, and low fabrication cost

Hilborn, E. H.

English

NASA Technical Reports Server

October 1970	 Brief 70-10476 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Visual Display Panel Functions as Computer Input/Output Device 
Step-Up 
Transformer 
I
Out of Phase - 
Low Voltage 
] 1JTa p
 1 
In Phase 1 Low Voltage Tap High Frequency 
ac Generator
Fire	 Probe 
_--1 
/ LL 
Erase
J\L 
Plasma Element 
Figure 1. Probe Drive
Matrix Surfaces 
A graphic visual display panel has been developed 
for computer data entry and readout. The device per-
mits information entry and erasure using a probe, 
and has an inherent storage capability for use on time-
shared systems. Data input need not be online. An 
operator can recognize and correct entry errors before 
introducing data into the computer. Other advantages. 
include direct display of computer input and output, 
simplicity, and low fabrication cost. 
Basically, the device consists of many gas filled 
cavities inside a glass plate with transparent covers. 
Ionizing the gas permits display of data read in or out 
of the computer. By maintaining the matrix of plasma 
elements at a sustaining voltage, data can be entered 
by supplying sufficient additional voltage to ionize 
selected matrix elements. An external probe fires any
selected element. Once fired, the element remains 
ionized after removing the probe. Phase reversal of 
the probe current supply enables the voltage to be re-
duced at a selected element at a point below the-sus-
taining voltage, thus causing selective erasure. The 
inherent memory features of the plasma elements per-
mit storage of the information until required by a 
computer. 
Figure 1 shows a method for implementing the probe 
drive. A high frequency ac generator, and step-up 
transformer provide cell sustaining voltages and in-
phase and out-of-phase probe drive voltages. The 
switch selects in-phase or out-of-phase voltage provid-
ing erase or write capabilities respectively. 
Figure 2, a nonconducting substrate, contains 
cavities formed by etching, drilling or other suitable 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned .rights.
https://ntrs.nasa.gov/search.jsp?R=19700000459 2020-03-17T00:31:48+00:00Z
Conducting Row 
Electrode
C.nritnr
Non-Conducting 
Substrate 
Transparenfr 
Cover Sheets 
CondL,	 -.
Figure 2. Cross Section of a Series of Plasma Elements 
techniques. These cavities are filled with an inert gas 
such as neon (typically with traces of nitrogen or 
carbon monoxide as additives) at a pressure about 
50 to 200 torr. Transparent, nonconducting cover 
sheets prevent escape of the gas and maintain the ap-
propriate gas pressure. Conducting • row electrodes 
(only one is shown) and conducting column electrodes 
are deposited on the exterior surfaces of the cover 
sheets; either or both the row and column electrodes 
must consist of transparent conductors to permit 
observation of the gas ionization in the cavities when 
voltage is applied. 
External electrodes help to increase the cell's use-
ful lifetime by several orders of magnitude. However, 
internal electrodes may be driven with direct current 
or low frequency alternating current. Since external 
electrodes are capacitively coupled to the cavity, they 
require high frequency alternating current on the 
order of several hundred kiloHertz for operation. 
This capability for capacitive coupling makes it pos-
sible to utilize an external probe for selective firing 
of the elements.
Notes: 
1. Although plasma elements with external electrodes 
have been used, elements with internal electrodes 
would also be possible, providing appropriate 
changes were made in circuit constants. Also, while 
the probe used passive RC networks, the use of a 
probe containing a unity gain amplifier could be 
used and would eliminate the requirement for a 
dropping resistor on the "write" position of the 
probe. Where only single analog quantities require 
entry, a linear array of elements could be used 
rather than the crossed matrix array. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Headquarters 
National Aeronautics 
and Space Administration 
Washington, D.C. 20546 
Reference: B70-10476 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: E.H. Hilborn

Electronics Research Center

(ERC- 10223) 
Brief 70-10476	 Category 0 1,09


Visual display panel functions as computer input/output device

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