From: In September 1973 Don Lancaster introduced his TV Typewriter. It =
would=20
display 2 pages of 16 lines of 32 characters each. There was a built in =
RF=20
modulator so you could connect it to any TV. The memory consisted of 512 =
bit=20
shift registers. The magazine article had a 6 page summary of the =
design. You=20
had to send off for the 16 page package of construction details. Radio=20
Electonics sold thousands of copies for $2.00 each. Southwest Technical Products (SWTPC) sold the printed circuit boards =
for the=20
TV Typewriter as they did for many of Don's projects.. In the late 1960s =
and=20
early 1970s Don had a construction article almost every month in Popular=20
Electronics or Radio Electronics. One of his more successfull =
product lines=20
was based on a Decimal =
Counting=20
Unit. In 1975 SWTPC introduced the TV Typerwriter II (CT-1024). Don had =
nothing to=20
do with that version and he will tell you so if you ask him about =
it. A surplus keyboard is used on this version of the TV Typewriter. Unit =
on the=20
cover has the homemade keyboard from the February issue.
By DON LANCASTER This construction project started out as a, very low cost computer =
terminal=20
for home use, but as it went together, we became aware of the many =
possible=20
non-computer uses for such a device, particularly since it is priced =
right. What=20
can you do with a machine that puts letters and numbers on an ordinary=20
unmodified TV set? Obviously, it's a computer terminal for timesharing services, =
schools, and=20
experimental uses. It's a ham radio Teletype terminal. Coupled to the =
right=20
services, it can also display news, stock quotations, time, and weather. =
It's a=20
communications aide for the deaf. It's a teaching machine, particularly =
good for=20
helping preschoolers learn the alphabet and words. It also keeps them =
busy for=20
hours as an educational toy. It's a super sales promoter, either locally or on a store wide basis. =
It's=20
easily converted to a title machine for a video recorder. It's a message =
generator or "answer back" unit for advanced two way cable TV systems. =
Tied to a=20
cassette recorder, it's an electronic notebook and study aid, or a =
custom=20
catalog. It's an annunciator for plant, schools, and hospitals that =
tells not=20
only that someone is needed, but why and where. And, if all that isn't enough, it's easy to convert into a 12 or 16 =
place=20
electronic calculator. You can also make a clock out of it, and, with =
extensive=20
modification, you can even make a 32 register, 16 place serial digital =
computer=20
out of the beast! Cost of the project? Around $120 for the basic unit. This is slightly =
under=20
two month's normal rental of commercial units that don't do nearly as =
much, and=20
less than 1/10 the cost of anything commercial you could buy to do the =
same job.=20
And we feel that this cost is finally low enough that a lot of new uses =
are now=20
not only possible, but reasonable as well. The low cost comes about by using the latest available =
semiconductors,=20
leaving the keyboard and case as flexible options, and working in kit =
form. Printed circuit boards and complete kits are readily available as are =
any=20
special or hard to get normally parts. A limited quantity of high =
quality=20
keyboards are also available from the same source. This is not the sort =
of thing=20
you'd want to try as a first electronic project, but if you are willing =
to=20
slowly and methodically work things out and carefully reason out any =
debugging=20
problems, you shouldn't have an unreasonable amount of trouble getting =
the thing=20
to work. Once you're past a certain stage early in the construction, the =
TV set=20
itself becomes a self testing display that greatly simplifies =
debugging. To make things easier, you can get a complete copy of the entire =
story that=20
includes additional design information, how it works, PC patterns, =
construction=20
details, etc. DO NOT ATTEMPT CONSTRUCTION WITHOUT THIS ADDITIONAL=20
INFORMATION! Construction is done in stages. Once each stage is tested, it is safe =
to go=20
into the next, progressively working up to a complete unit. The basic =
machine=20
we'll show you works from a keyboard or a set of six switches and a =
pushbutton.=20
Thanks to the plug in construction, low cost add on circuit boards can =
let you=20
talk to a computer or a cassette recorder, or adapt the unit for 12 =
place=20
calculation. These add ons will be picked up later if enough readers =
seem=20
interested. They're not needed for most of the possible applications of =
this TV=20
Typewriter. Complete specs appear in Table 1. The basic device generates and =
stores 512=20
characters, arranged as sixteen lines of 32 characters each. A second =
page of=20
characters is easily added internally to bring the total up to 1024 =
characters.=20
For more storage, a C90 cassette can store well over a hundred pages, so =
the=20
total capability is quite large. The characters available are standard =
ASCII=20
ones that include the capital letters, numerals, and most =
punctuation. The TV Typewriter is self powered and contains its own miniature TV=20
transmitter which simply clips onto the antenna terminals of an =
unmodified TV=20
tuned to an unused channel. Several TV's may be driven simultaneously, =
and a=20
direct video output is also available for industrial and experimental =
uses.=20
While any TV can be "borrowed" and used with the typewriter, small, high =
quality=20
portables give the nicest presentation, and slight size and position =
adjustments=20
can further help the appearance, although they are not needed. The characters are added one at a time and normally go on the screen =
just=20
like you were typing. This is done by providing the proper ASCII =
character code=20
on seven input lines and tripping an eighth "key pressed" line to enter =
the=20
character. A winking cursor tells you where the next character is to go, =
but you=20
can turn this off if you want to. Should the screen get filled, the =
machine=20
starts over again on the top, rewriting over the old message. Besides the normal operation, you have a complete editing capability. =
You'=20
can move the cursor either direction anywhere you want and then change =
only the=20
characters or words you wish to, thus editing something you already have =
on the=20
screen. This nicely handles mistakes without having to start over again. =
A=20
REPEAT key is available for putting down a group of identical characters =
or=20
getting to a given position in a hurry. There's a KEEP CHANGE switch to =
protect=20
what you have written while you are moving around, and you can home the =
cursor=20
to the upper left either by itself or erasing the whole picture on the =
way.=20
Other switches control the direction the cursor goes, which page is =
being=20
displayed, and optionally whether the mode will be a full screen one for =
typewriter use or a line scan one for calculator use. Computer people would call this a parallel input system with off line =
editing. A single machine command is available; this is the LINE FEED. =
Thus, any=20
CTRL key moves you down a line. Other remote commands are easily added, =
but were=20
left off to hold the cost down. The contents of the memory can be =
retransmitted=20
with simple circuit modifications, and the whole system is bus-oriented =
to allow=20
all sorts of add ons without major circuit rework. Character input rate is asynchronous and up to 30 characters per =
second, thus=20
making the beast three times faster and compatible with the industry =
standard=20
ASR 33 teletype. Hard copy is via cassette recorder or Poloroid, =
photos. To keep things as simple as possible, the circuit is arranged like a =
set of=20
snap together blocks. This way, the only interconnect wiring consists of =
the=20
line cord and the 300 ohm twinlead output. Since the interconnect wiring =
is=20
locked into the board and 60 pin connector system, the biggest single =
headache=20
and potential error source is eliminated. Fig. 1 shows the basic blocks. The MAINFRAME contains a power supply =
of + 12,=20
+ 5, 5, and 12 volts; the control switches; the RF modulator; the =
internal test=20
system; and connectors for both the keyboard and the other boards in the =
stack. There are three other essential boards. The MEMORY board is the most=20
important and the most complex. It contains a dynamic MOS (Metal Oxide=20
Semiconductor) shift register that stores 512 words of 6 bits each. It =
also=20
holds a single line memory; a character generator; and an output video =
register.=20
We'll see later that the single line memory is needed to get each =
character back=20
eight times in sequence for eight successive TV scans. For a page A memory, you need all of this board. The additional page =
B memory=20
does not need a new single line memory, character generator, and output =
video=20
register, as it can borrow the one in the page A memory when the second =
page is=20
in use. This is called bus organization. The character generator will =
respond to=20
anything that is enabled on the bus, be it page A memory, page B memory, =
a=20
calculator add-on, or whatever. Of course, we have to be careful to only =
enable=20
one possible source of characters at a time, but this is easy. We can =
also use=20
the bus optionally to output characters to the outside world. The output of the memory board also contains a video combiner that =
assembles=20
the character video, sync signals, and the internal test signal into one =
composite video output. This output may either be used directly or =
routed to the=20
RF modulator for clip on operation of an unmodified TV. It can be =
optionally=20
flashed or blinked. The TIMING board contains a crystal divider and TTL (Transistor =
Transistor=20
Logic) countdown chain that generates all the needed signals to run the=20
typewriter in proper sequence. It does not normally use interlace, but =
the=20
timing chain is split so that the somewhat more complex TV =
full-interlace system=20
can be added if you need this sort of thing for video titling. There are =
two=20
principal areas to the timing board, the MAIN timing, and the DERIVED =
timing.=20
The main timing is the continuous waveforms obtained off the crystal =
divider,=20
while the derived outputs combine portions of the main timing signals =
into=20
properly coded signals needed to run the rest of the typewriter. Two =
examples=20
are the composite sync signal and a blinker used for flashing, cursor =
winking,=20
and repeat functions. The third essential board is a CURSOR board. Anyone who ever tried to =
design=20
and debug a simple one of these will easily understand why it is called =
a cursor=20
board. Anyway, the cursor keeps track of where the next character is to =
go; runs=20
the winking line that shows the character position; controls entry of =
the=20
character; and optionally sets up characters for output. It also =
contains an=20
input conditioner, and debouncer and a detector for CTRL commands that =
tells the=20
typewriter to carriage return rather than enter a character. Many cursor systems are extremely complex. This one is relatively =
simple in=20
that it uses a phase shift counting technique. The cursor has a =
continuously=20
running counter just like the main timing chain does. Its output drops =
suddenly=20
in some relative position, indicating where the next character is to =
go. To back the cursor up, we throw in another count pulse. To run it =
forward, we=20
hold back one normal count pulse. Thus, the relative position or phase =
of the=20
cursor counter advances or backs up with respect to the system timing. =
Actually,=20
to go forward, we hold back two normal system timing pulses and throw in =
a new=20
one. This buys us a simplification of circuitry, but still ends up with =
the same=20
result. An ADD SUBTRACT switch on the mainframe controls the cursor direction =
for=20
editing. LINEFEED is handled by adding and removing the proper number of =
counts=20
in the proper position in the cursor counter so that the new position is =
reached. Just like most typewriters, the linefeed always returns to the =
left=20
hand side. And, this is about all you need for a normal parallel entry type of =
TV=20
typewriter. One possible optional board is a MODEM or frequency shift =
keying=20
interface. This would use a MOS chip and some TTL to convert to or from =
a serial=20
tone input, suitable for computer or telephone line communication. A =
cassette=20
recorder will work just as well with the modem for electronic notebook =
use. Another possible add on makes the typewriter into a calculator. This =
is done=20
by converting the scan from a complete frame to a single line of =
numerals and=20
would use a surplus calculator chip to provide the familiar calculator=20
functions. If you already have or need the TV typewriter for something =
else,=20
this add on is far cheaper than a conventional calculator would be, and =
its=20
display would be obviously larger and more readable. Or, you can add most anything else you want onto the machine by =
tieing into=20
the bus oriented lines (b1 through b6). For instance you can think of =
the memory=20
as sixteen registers of 32 numbers each, and those numbers are decimal =
numbers=20
plus, not bits! With six bits per word, you can store 10 possible =
numerals and=20
54 machine commands in any word! Or, you can split the registers into 32 =
registers of 16 decimal numbers each, building your own computer or =
programmable=20
calculator. Of course, this computer add on is very much an advanced experimenter =
project, but it really doesn't take much more than a double handful of =
TTL to=20
pull it off. While such a computer will be relatively slow (around a 33 =
ms cycle=20
time), it does provide an extremely accurate and very low cost computer=20
approach, particularly when you are working directly with BCD numbers =
instead of=20
binary. Before we turn to the actual circuitry, some basics of what a =
character is=20
and how it can get on a TV screen is in order. Lets start with the=20
characters: If we had six possible binary bits of either 1 or 0, we would have =
sixty four=20
different possible combinations ranging from 000000, 000001, 000010, . . =
.=20
through to 111110 and finally 111111. These 64 different states can =
represent=20
all the capital letters, all the numbers, a blank, and most punctuation, =
following the standard ASCII code. In the TV Typewriter, all of the six =
bits of=20
this code must be presented at once or in parallel form, and this is the =
only=20
code the circuitry shown can use. Other codes can be converted to ASCII =
before=20
going into the TV Typewriter. A seventh bit is used to separate =
characters from=20
internal commands. Our final presented character consists of an array of 5 x 7 dots. =
Since it=20
only takes 6 bits to store a coded character and at least 35 bits to =
store a=20
generated one, its obviously much better and cheaper to generate the =
characters=20
after they are stored, rather than before. For other keyboards and encoders, the typewriter gives you lots of +5 =
and a=20
choice of +12 or -12 volts at relatively low current. The original Radio =
Electronics ASCII encoder needs the +12; a mechanically encoded keyboard =
will=20
only need +5, while a MOS encoded keyboard probably will need +5 and -12 =
volts. A limited quantity of suitable keyboards is presently available from =
the kit=20
source. Other sources of input material include computers, calculators, =
the=20
phone line, or a cassette recorder. Many of these signals will be in =
serial or=20
one bit at a time form and have to be changed to the parallel ASCII =
code. This=20
takes an add on board using a MOS terminal receiver chip. Regardless of =
the=20
source, your input must be in parallel form when presented to the =
typewriter,=20
with a "1" near but not exceeding the internal +5 and a "0" near but not =
going=20
below ground. Internal debouncing is provided on the cursor board for =
manual=20
keyboard entry. To use an unmodified TV, we have to build a miniature transmitter and =
arrange=20
the signals so they compare as closely as possible to a normal broadcast =
set of=20
scanning standards. This way, any TV can be driven by the typewriter =
simply by=20
clipping onto the antenna terminals and tuning to an unused low =
channel. A TV starts in the upper left hand corner and sweeps a dot rapidly to =
the=20
right and slowly downward, taking around 62 us to get across the screen =
and 33=20
ms to get to the bottom. It then repeats the process again and again, =
presenting=20
a series of dots that assemble into a series of still pictures that the =
tube=20
phosphor and your eye integrate to get the effect of a complete and =
usually=20
moving picture. Brightness is changed on each dot by controlling the picture tube's =
cathode=20
current, which in turn follows the input RF signal seen at the antenna=20
terminals. Very low signal is seen as white. The stronger the signal, =
the=20
blacker the picture. The sync signals are the strongest of all, or =
"blacker than=20
black", and are used to synchronize the scanning of the television set =
to the=20
transmitted signal. To provide sync, we need one horizontal sync pulse at the beginning =
of each=20
scan line, and one vertical sync pulse for the beginning of each frame. =
To keep=20
things simple, we make all the frames identical in the TV Typewriter =
instead of=20
using interlace. Interlace has no advantage on a stationary message =
presentation=20
and simply adds parts. If you have to you can easily add it for video =
titling or=20
other places where you must superimpose the TV Typewriter's output onto =
an=20
existing program. We assign 48 possible character positions across the TV screen, but =
we only=20
use 32 of them. The remaining 16 allow for retrace and the extreme =
overscan used=20
on economy TV's. We assign 12 scan lines per row of characters. The =
uppermost=20
scan line is blank except possibly for a winking cursor that appears as =
a bar=20
above the next character to get input. The next 7 lines form the =
character as a=20
series of dots 5 dots wide by 7 dots high, and the final 4 lines are =
blank.=20
These allow for the space between character lines. We likewise assign 22 possible character lines but only use 16 of =
them, this=20
time saving 7 for vertical retrace and overscan. By picking the right =
timing=20
frequencies, we obtain a horizontal rate thats so close to the normal =
rate the=20
TV doesn't know the difference, and a vertical rate of exactly 60 Hz. =
The latter=20
is especially important to keep hum bars out of the display. Since each =
frame is=20
stationary and ends with a bunch of blanks, Equalizing pulses are =
neither needed=20
nor used. Each character takes six bits of storage, arranged as one parallel 6 =
bit=20
word. The storage is used to hold the character from time of entry until =
it is=20
no longer needed, which can range from seconds to days. For a single =
page memory=20
of 512 characters, we use six 512 bit recirculating MOS shift registers. =
These=20
go around once each TV frame. The timing and cursor boards together =
decide where=20
in each of the six registers a new character is to go. Once in memory, =
the=20
character stays in the same relative slot until it is cleared or =
replaced. The=20
memory is violatile, meaning that you lose the message if power drops =
for more=20
than a half a second or so. Note that an ASCII blank is 100000. All 1's is a "?" and all 0's is =
an "@".=20
This is helpful when troubleshooting, for its rather difficult to get a =
totally=20
blank screen by accident. On the other hand, this means we have to be =
careful=20
when we clear our memory to erase the screen. Here, we purposely have to =
set up=20
the 100000 code. One way to do this, is to hold down the keyboard's =
space bar=20
during the clearing process. A better way is to remove the keyboard =
encoder=20
power (via the UNCLEAR or not clear line from HOME switch S6) from the =
encoder=20
to get all 0's out. Then a "1" can be force fed to the a6 input line to =
set up=20
the proper code. This gives us a onebutton clearing operation. Other =
schemes can=20
easily be worked out, but the essential thing is that the 100000 code =
gets set=20
up during the time you want to erase what you have. We normally put a character into memory and leave it there for a =
relatively=20
long time. The memory usually is in a recirculate mode where its own =
output is=20
connected 'internally back to its input. The memory is a serial device =
the bits=20
take turns coming out one at a time, and 512 pairs of clock pulses are =
needed to=20
turn the memory over exactly once. The memory is normally in the recirculate mode. We keep it there if =
we are=20
using the other page or if we have our KEEP CHANGE switch in the KEEP =
position.=20
We also force it to recirculate if a CARRIAGE RETURN command (a6 and a7 =
=3D 0)=20
arrives, for, just like a typewriter, we don't want to enter anything =
while the=20
carriage goes back to the beginning of a line. So where do we get our characters? The simplest and far cheapest =
source is=20
from six switches and a pushbutton, arranged to get us + 5 for a "1" and =
ground=20
for a "0" and set up so the pushbutton gives you a sudden + 5 to ground=20
"Keypressed" output. This is handy (almost essential) for testing, and =
can be=20
used for message generation, although it takes quite a bit of practice =
to get=20
any speed. A keyboard is the next best bet, such as the low cost keyboard in the =
February 1973 issue of Radio Electronics, and its low cost companion =
ASCII=20
encoder (April 1973). Many of the surplus keyboards offered in the back =
pages of=20
Radio Electronics can also be either used directly or readily =
adapted. The input code must be in ASCII. Any keyboard that consists of one or =
two=20
make contacts per key must be converted in a suitable encoder, again =
such as the=20
low cost ASCII encoder described in the March 1973 issue of Radio =
Electronics.=20
Further, the ASCII output must never exceed the internal + 5 volt supply =
of the=20
typewriter, nor should it go below ground, even by a small amount. Jumpers on the timing band allow for selection of 12 possible display =
positions so that internal TV adjustments need not be changed. We use raster scan dot matrix characters providing an array of 5 dots =
wide by=20
7 dots high for each character with one "undot" between characters for =
spacing.=20
Seven passes of the TV raster are needed to generate each line of =
characters.=20
This says we must borrow one line's worth of characters (32) from the =
memory and=20
put it into a new line register memory, use it over again at least seven =
times,=20
and then later on, go get a new line of characters. To do this, we need =
a line=20
memory, a single IC consisting of six 32 bit recirculating shift =
registers. Let's go through a typical scan and see what happens. Most of the =
circuitry=20
is shown in Fig. 2. Suppose we just retraced to the upper left hand corner. We're now on =
line 1=20
of the top of the characters. On line No. 1, our line register is =
connected to=20
the memory and it samples the next 32 characters to be presented. The =
main=20
memory thus fills the line register. For the next twelve scans, the =
memory is=20
idle, but the line register brings the same characters back over and =
over again.=20
On scans No. 2 through No. 8, the character is actually generated. The =
line=20
register drives a character generator. The character generator is also connected to logic that tells it =
which part=20
of each character it is working on. The output of the character =
generator goes=20
to an output register that converts the characters into actual video Since line No. 1 is supposed to be all blanks, the character =
generator is=20
told this and we get all blanks, except possibly for a brief cursor =
winking=20
bar. On the second scan line, we again clock the line register 32 times, =
letting=20
it go once around. The main memory just waits. This time, the character=20
generator is told to work on line No. 2 and please put down the top row =
of dots=20
on each character. For instance, if a "T" comes up, we get five "1's" in =
a row.=20
An "S" would be 01110 and so on. As the TV scans across, each top row of =
dots=20
for each following character is put down. On the next pass, we again clock the line register 32 times. This =
time, the=20
second row of dots gets output, with a "T" being a 00100 and an "S" =
being 10001,=20
and so on. Lines No. 4, 5, 6, 7, and 8 are handled the same way, with =
the=20
character generator working on the line it is told to and the line =
register=20
going once around for each line. By the end of the eighth line we have =
put down=20
all the dots we need for a line of 32 complete dot matrix characters. =
The=20
circuitry is blanked for the next four scan lines, providing us with a =
space=20
between character lines. On line No. 13 (a new line "1"), our main character memory is once =
again=20
clocked 32 times and the line register is simultaneously clocked. This =
fills up=20
the line register with a new set of 32 characters. The same operation =
repeats=20
for each of the sixteen rows of characters that we want to put down. Notice that the timing runs in bursts and is not continuous. Thus, =
the line=20
register runs for 32 counts and waits 16 for retrace and so on. The =
memory does=20
the same thing, but only on every twelfth line during the active scan. =
Carefully=20
established internal timing delays take care of settling times between =
memory,=20
line register, character generator, and the final video generating =
output=20
register. The output register converts the five parallel outputs of the=20
character generator into seal, high speed video. So far, we've assumed that we were using the page A memory with the =
page A=20
character generator. Thanks to the memory bus (bl through b6) we can =
connect=20
anything we like to the character generator, including the page A =
memory, the=20
page B memory, or anything else we want to hang on these lines. To run page B, we simply disable the page A memory and enable the =
page B=20
memory's output. The handy thing about bus organization is that no =
complex=20
switching is involved. Whatever is enabled gets connected to the =
character=20
generator; other things tacked on just sit there. The only restriction =
is that=20
we have to enable only one character source at a time. We can also use =
the same=20
memory bus optionally to output characters to a computer, a cassette =
recorder,=20
or a phone line. TABLE I Internal: RF frequency (trimmer capacitor) EXTERNAL: ONOFF Don Lancaster's TV Typewriter
September =
1973 Cover=20
Image
Gernsback Publications, Radio Electronics publisher, when out of =
business in=20
late 2002 after 90 years in business. Here is the article text.
TV TYPEWRITER
This character generator and your TV set form a computer terminal,=20
educational toy or display device. Basic details are here. Full an =
complete data=20
is yours when you need it.
Specs of the unitOrganization of the instrument
In normal operation, each character entry moves the cursor =
over=20
one character. When it gets to the end of the line, it star again on the =
next=20
line. When it gets to the bottom of the page, it starts again at the =
top. A=20
CLEAR or HOME override also moves the cursor to the upper left hand=20
position.Some basics
Interfacing with the TV
The only time we =
actually=20
enter a character is once when the cursor board tells us it is the right =
time,=20
then only if we are working on this page, want to change the character, =
and are=20
not trying to return the carriage.About keyboards
Character generation
About the memory bus
This way, with suitable add ons we have a choice. We =
can=20
send one character at a time directly from the keyboard, or we can send =
an=20
entire page at a time from the memory. The latter is faster and more =
complex but=20
has the advantages that you can fix all the mistakes first and don't tie =
up=20
nearly as much outside equipment
COMPLETE SPECIFICATIONS TV TYPEWRITER
STORAGE:
1024 Characters arranged as 2 pages of 16 lines of =
32=20
characters each.
OUTPUTS:
RF Output tuneable from channel 2 through 5; clips =
directly to the antenna terminals of one or more unmodified =
television=20
sets. Optional positivewhite video output.
INPUTS:
Parallel, TTL compatible, ASCII character code =
(Table II)=20
is in­put with positive logic on six lines; a seventh =
keypressed=20
line is suddenly brought to ground to input character, Internal=20
de-bouncing. The full 8bit ASCII code may also be used as an =
input. If=20
done, any CTRL input will be interpreted as a combined CARRIAGE =
RETURN and=20
LINE FEED, CTRL output available for code extension.
FORMAT:
Begins in upper left HOME position and proceeds as =
in=20
normal typing. Carriage return and linefeed automatic at end of =
line. At=20
bottom of screen, jumps to upper left HOME position and rewrites =
over old=20
text.
EDITING:
Winking cursor indicates next character position. =
Cursor=20
may be blanked and may be independently moved in any direction =
with or=20
without changing text. One or more letters may be easily changed =
at any=20
time.
TIME BASE:
Internal, crystal controlled TTL divider. Basic =
video=20
clocking rate =3D 4.562 MHz. 15,840 kHz noninterlaced horizontal =
scan rate;=20
60Hz vertical scan rate. Easily converted to full interlace for =
Video=20
Recorder titling applications.
MEMORY:
512 word by 6 bit MOS dynamic storage, bus =
oriented=20
for easy page conversion, optional memory output, and optional =
extension=20
to calculator, computer, and other functions.
CONTROLS:
Position =
(Jumpers4=20
horiz; 3 vert for 12 possible locations.)
PAGE OR LINE SCAN =
KEEPCHANGE=20
memory protect
A or B page select
REPEAT Or SINGLE=20
character
HOME or RUN cursor location
CURSOR ONOFF=20
ADDSUBTRACT cursor direction
CONSTRUCTION:
Modular motherdaughter boards. Mother board =
contains=20
power supply, RF modulator, and control switches. Timing board, =
cursor=20
board and one or two memory boards snap on as a stack. Addons such =
as=20
calculator and MODEM FSK unit snap onto same stack; not included =
in basic=20
unit. 33 integrated circuits, of which 8 are MOS LSI.
SIZE:
7"x8'/z"x3",not including keyboard or=20
case.