THE REVOLUTIONARY NEW WAY TO PRACTICE
MORSE CODE RECEPTION. AN UNLIMITED
SUPPLY OF PRECISION MORSE AT THE TURN
OF A SWITCH, PLUS BUILT-IN OSCILLATOR
FOR SENDING PRACTICE.
which are needed to get the full enjoyment from real-life
operating. Its wide speed range means that even experts
can use Morse Tutor to keep in trim or as a refresher
course.
HOW TO LEARN MORSE WITH THE DATONG TUTOR
Sends a continuous stream of precision Morse
in five character groups which never repeat.
Variable speed and variable delay between
characters for optimum learning efficiency.
Letters only, numbers only, or mixed.
Built-in tone oscillator for sending practice (key
required).
Earphone socket for private listening.
Eleven IC, CMOS circuit for long internal battery
life.
PRECISION MORSE
The Datong Morse Tutor sends a continuous stream of
precision Morse Code in random five letter groups. Its
sending is impeccable; it never repeats and it never tires.
You can select letters only, numbers only, or letter and
numbers mixed, at the flick of a switch.
OPTIMUM LEARNING TECHNIQUE
Best of all not only can you vary the basic sending speed
from 6.5 to 37 words per minute, you can also increase
the delay between letters from the "correct" value (3 dot
periods) to a maximum of over 3 seconds.
This delay facility means that right from the start you can
learn each letter and number as it ought to be learnt, that
is with the dots and dashes within a letter fast enough to
form a complete sound pattern, but with a long delay
between each letter. As you improve you simply reduce
the delay between letters.
USES YOUR TIME TO BEST ADVANTAGE
Skill at Morse reception only comes with practice and this
uses up valuable leisure time. With Model D70 you can
make every minute count because you can tailor the level
of difficulty exactly to your own ability.
Moreover you are no longer tied to someone else's
timetable. Morse Tutor is available at any time day or
night so you can snatch a few minutes practice whenever
it suits you. This way your practice sessions can make
use of time which would otherwise be wasted, while
travelling for example.
ALWAYS FRESH
Unlike tapes and records whose sequence becomes
familiar surprisingly quickly, the Morse Tutor never repeats
the same sequence twice. This means you don't have to
ration the supply to avoid wasting it.
LEARN WITH CONFIDENCE
Morse Tutors' calibrated controls mean there will be no
doubt about when you are up to examination speed. With
today's examination fees it pays to pass first time.
AFTER THE MORSE EXAM
After Morse Tutor has helped you to pass the Morse
Exam it will painlessly help you to the still higher speeds
The key to learning Morse is to learn each character as a
complete sound pattern not as a set of individual dots and
dashes. It is important also to be able to receive Morse
reasonably well before you begin to practice sending.
Start with Morse Tutor set to between 8 and 12 words per
minute but with maximum delay between characters. This
way you learn the correct rhythmic sound of each
character in the code list. As you become familiar with the
code, gradually reduce the delay between letters. Ideally
the speed should always be slightly faster than you are
able to read comfortably.
Many short practice sessions are much better than few
long ones. Take advantage of Morse Tutor's portability
and personal earpiece to snatch as many practice
sessions as possible. You can learn Morse with minimum
disruption to your normal activities by using time which
would otherwise be wasted for example while travelling to
and from work.
Once you have learnt the basic code and can recognise
the characters from memory, your main practice should
consist of writing down the output from Morse Tutor. Use
longhand right from the start rather than printing,
otherwise as you progress your ability to copy Morse will
outstrip your speed of writing. It is also beneficial to listen
to Morse Tutor's output even at times when you are
unable to write it down. This helps you to recognise the
"tune" of each character and to split up the continuous
stream into separate characters.
Do not be discouraged if your progress appears to come
to a halt at various stages. This is quite normal and in fact
is normally a prelude to a significant jump in receiving
speed.
When you have reached a speed of about six words per
minute you are ready to begin sending practice. Simply
plug a conventional Morse Key into the *KEY' jack on the
rear panel of Morse Tutor. This disables the automatic
sending circuitry and the unit will produce a tone
whenever the key is pressed /(the key should close a
contact when pressed).
INTERNATIONAL MORSE CODE
Morse code comprises a stream of dots and dashes. If the
duration of a dot represents one time unit, a dash is three
units, the space between dots and dashes within a
character is one unit, the space between letters in a word
is three units, and the space between words is seven
units.
When the 'DELAY' control is set to the 'CALIBRATE'
position (fully clockwise) Morse Tutor produces Morse
with the above timing and in five character groups. As
extra delay is introduced between letters the delay
between words becomes just twice the delay between
letters. Timings within each letter are determined only by
the 'SPEED' control.
The basic Morse characters are given below in the form of
dots and dashes. When saying them either aloud are
mentally use "dit" to represent a dot and "dah" for a dash.
Letter C for example is pronounced dahdidadit. It is
important to learn the code as sounds not as visual
patterns.
A ·– N –· 1 ·––––
B –··· O ––– 2 ··–––
C –·–· P ·––· 3 ···––
D –·· Q ––·– 4 ····–
E · R –·– 5 ·····
F ··–· S ··· 6 –····
G ––· T – 7 ––···
H ···· U ··– 8 –––··
I ·· V ···– 9 ––––·
J ·––– W ·–– 0 –––––
K –·– X –··–
L ·–·· Y –·––
M –– Z ––··
AUDIO NOTE
The frequency of the audio tone can be altered if desired
by adjusting the preset potentiometer labelled 'NOTE' on
the printed circuit board. To open proceed as described
under "battery replacement".
BATTERY REPLACEMENT
When Morse Tutor produces all dots or all dashes the
battery should be replaced.
First switch off the unit. Then remove the top two screws
on both front and rear panel and lift off the upper half of
the case. The battery can then be replaced. Take care to
observe the correct polarity. WARNING: When replacing
the panel screws take care not to strip the threads by
overtightening.
SERVICE INFORMATION - MODEL D70
THE CIRCUIT AND SERVICE INFORMATION SUPPLIED IS CONFIDENTIAL AND
FOR USE BY DATONG AGENTS ONLY.
1. Refer also to circuit diagram, data sheet, PCB layout.
2. Dismantling
Remove the eight screws holding both front and rear panels. This allows the
top half of the case to be removed. To remove the PCB remove the four screws
through the PCB. Leave the panels and controls soldered to the PCB leads.
3. Circuit description
A 'noisy' clock oscillator (IC10a, b) clocks the address counter (IC8, IC9)
for the PROM (IC7) at a random rate. When information for the next character
is required a brief positive pulse is generated by Q4 which powers up the
PROM. Information at the PROM's outputs (pins 1, 2, 3, 4, 5, 6, 7, 9) is
then latched into IC5 and IC6 by a strobe pulse from pin 10 of IC3a. The
strobe pulse is slightly delayed from the power-up pulse by R8 and C5. The
strobe pulse is very short (mainly determined by R9 and input capacitance of
pin 10 of IC2b).
Information captured by IC5 determines the length of the next character.
Information stored in IC6 (shift register) determines the dot-dash sequence.
A 'low' into the preset inputs of IC6 signifies a dash and a 'high' dot.
Characters are read out at a rate determined by the main timing oscillator
(IC1a and b) under the control of the "SPEED" control. The square wave from
IC1b is converted into a single dot-plus-space (one cycle of the clock) or a
dash-plus-space (two cycles of the clock by IC2a and IC3b). When pin 4 of
IC2a is low dashes are produced and dot when pin 4 is high.
During the read out of a character IC5 counts up by one for every dot or dash
from the number originally loaded into it by the strobe pulse. When the
number reaches binary eight pin 2 goes high. This turns off the audio output
via R3 and after a delay determined by VR2 and causes D on IC2b to go high.
Furthermore pin 4 of IC2a is forced high via IC3c so that a "silent dot" is
produced. At the end of this "silent dot" Q of IC2b goes high and data for
the next character is called up from the PROM. The "silent dot" in effect
constitutes the inter letter space (3 time units) while the extra delay (if
any) selected by VR2 and C6 adds to the inter letter space.
After five interword spaces have been counted by IC4 its pin 2 goes high and
forces the production of a "silent dash" (via IC3d). It also presents a high
at pin 3 of IC5 during the load pulse and this transfers immediately to pin 2
after the "silent dash" thereby causing the letter to be followed immediately
by a "silent dot". The two together constitute the seven time unit interword
space.
When letters are being produced the combination IC8/IC9(a) counts cyclically
down in binary from 26 to 1. The state zero exists only for the time
required for IC8 and IC9(a) to self reload to 26. Any fault in this
resetting will cause address zero to be accessed and this will produce the
illegal character dah-dah-dah-dah.
With number generation IC9(a) remains held with pin 1 high and IC8 counts
down from 26 to 17. Here the never-normally-accessed address is 16. If, due
to a fault, it is accessed the illegal character produced is dah-dah-dit-ditdah.
In the "numbers" mode D7, D6 and D5/R12 ensure that IC5 is always loaded with
binary "3". The character length then being 8-3 = 5.
In the "mixed" mode IC9(b) extends the address counter by an extra bit and
its output determines whether the next character is to be a number or a
letter.
4. Typical faults
The following faults have occurred at various times in the past.
(a) Accidental unsoldered feed through pins or IC top pins can cause illegal
letters to be produced.
(b) Some specimens of IC10 have resulted in random clock pulses which are
too narrow to clock IC8 correctly. This results in the illegal
addresses 0 and 16 being accessed. The pulse train at pin 11 of IC10(b)
should look symmetrical about 2.5 volts.
(c) If Q4 does not turn fully "off" Q3 can remain slightly "on". When VR2
is set to a high value this can cause a very long, even an infinite
delay to occur as charge leaks through Q3 faster than VR2 can supply it.
R20 was added later to avoid this.
5. Other points
(a) Reducing C1 allows faster sending speeds to be achieved.
(b) Adding a jack to the rear panel to allow an external supply to be used
can short out the regulator if an uninsulated jack is used. This is
because the back panel is at +5 volts. If this happens the TTL PROM
will probably be damaged.
(c) If an output for a tape recorder is required from the earphone jack a
resistor (say 100R) is required to maintain a DC path for collector
current in Q2.
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