Hal Communications DKB-2010 User manual

HAL DKB-2O1O DUAL MODE KEYBOARD
TECHNICAL MANUAL
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WARRANTY
HAL Communications Corp. warrants that all factory-assembled DKB-2010 Dual
Mode Keyboards shall be free of defects in materials and workmanship under
normal use and service for a period of one year from the date of shipment, and
further warrants that all parts supplied with DKB-2010 kits shall likewise be free of
such defects for the same period.
In fulfillment of this warranty, HAL Communications Corp. will, at its option, repair
or replace at no cost except for transportation expenses any factory-assembled
keyboard (or, in the case of kits, any component) verified to be defective, provided
that written notice of such defect is given during the warranty period.
Please do not return your keyboard or components to the factory until you have
sent a letter of notification and
have received a written return authorization.
This warranty is and shall be in lieu of all other warranties, whether expressed or
implied, and of all other obligations or liabilities on the part of HAL
Communications Corp. resulting from the installation or use of this keyboard.
The foregoing warranty is completely void for all keyboards and keyboard
components which have been damaged, abused, modified, or improperly installed
or operated.
**********************************************************
Copyright © 1974 by HAL Communications Corp., Urbana, Illinois.
Printed in the U.S.A. All right reserved. Contents of this
publication may not be reproduced in any form without the
written permission of the copyright owner.
November, 1978 Printing
November, 2015 Reprint DC7XJ
________
NOTE: Inverted states – usually written for example as "HERE IS" – are shown in blue in this text.

1
TABLE OF CONTENTS
Specifications ........................................................................... 4
Section I: General Information
1.1 Description ....................................................... 6
1.2 Instrument Identification .................................... 6
1.3 Accessories Furnished ........................................ 7
1.4 Manual Preview ................................................. 7
Section II: Installation
2.1 Initial Inspection ................................................ 8
2.2 Preliminary Checkout .......................................... 8
2.3 CW Transmitter Keying Connections .................... 8
2.4 RTTY Loop Connections ..................................... 10
2.5 Audio Output Connections .................................. 12
Section III: Operating your Keyboard
3.1 Introducing ....................................................... 13
3.2 RTTY Operation ................................................. 13
3.3 Morse Code Operation ....................................... 15
Section IV: Theory of Operation
4.1 Introducing ....................................................... 16
4.2 General Operating Principles ............................... 16
4.3 Circuit Analysis .................................................. 17
4.4 Scanning Keyboard Encoder ............................... 19
4.5 ROM Code Converter ......................................... 20
4.6 Storage Buffer ................................................... 20
4.7 RTTY Control and Decoding Circuit ...................... 21
4.8 Shift Register and Control Circuit ........................ 22
4.9 RTTY Encoder and Loop Interface ....................... 25
4.10 RTTY Timing Chain ........................................... 27
4.11 RTTY Character Counter .................................... 28
4.12 Morse Character Generator ................................ 28
4.13 Morse Output Control ........................................ 31
4.14 Quick Brown Fox and ID Control ........................ 32
4.15 Identifier .......................................................... 33
4.16 Three-Character Sequencer ................................ 34
4.17 Power Supply ................................................... 34
4.18 Character Codes ............................................... 35
Section V: Assembly Instructions ............................................ 40
Section VI: Maintenance .......................................................... 45
Section VII: Parts List .............................................................. 57
Section VIII: Diagrams .............................................................. 60
Extended Memory Option
1. Introduction ..................................................................... A1
2. Installation ...................................................................... A2
3. Operating Instructions ...................................................... A3
4. Theory of Operation ........................................................ A4
Schematic ............................................................................ A5
Key Buffer Timing ................................................................ A6

2
ILLUSTRATIONS
Figure 2.1: Typical Connection for Cathode Keying ........................................ 9
Figure 2.2: Typical Connection for Grid-Block Keying ..................................... 10
Figure 2.3: Typical Loop Circuit Connection .................................................. 10
Figure 2.4: Connection for Loop Circuit with Negative Lead Grounded ............ 11
Figure 2.4a: Plug Preparation ....................................................................... 11
Figure 2.5: Bridge Polarity Protection Circuit ................................................. 12
Figure 3.1: Location of Controls and Keys ..................................................... 14
Figure 4.1: MM5740 Keyboard Encoder Integrated Circuit .............................. 18
Figure 4.2: Shift Register Waveforms for Transmission of the Letter "F" .......... 24
Figure 4.3: Shift Register Control Signals for Morse Operation ........................ 25
Figure 4.4: Generation of the Letters-Shift Code ........................................... 26
Figure 4.5: Generation of the Figures-Shift Code ........................................... 26
Figure 4.6: Morse Clock and Decoder Waveforms .......................................... 29
Figure 4.7: Production of Dots by the Morse Character Generator .................. 29
Figure 4.8: Production of Dashes by the Morse Character Generator ............... 30
Figure 4.9: Suppression of Dot at End of Character to Produce Intercharacter
Space ....................................................................................... 31
Figure 4.10: Development of Clock Pulses for Automatic Character Sequencers 33
Figure 5.1a: Rear Panel Component Placement
Figure 5.1b: Matching Transformer and Terminal Strip Details
Figure 5.1c: Rear Panel Wiring
Figure 5.1d: Wiring Detail for T301
Figure 5.2: Installation of Power Cord Strain Relief
Figure 5.3a: Top Panel Component Placement
Figure 5.3b: Top Panel Wiring
Figure 5.4: Wiring Harness Placement
Figure 5.5: Assembly of Cabinet End Panels
Figure 5.6: Space Bar mounting detail
Figure 5.7: Integrated Circuit Orientation
Figure 5.8: Mounting the MJE521 Power Transistor
Figure 5.9: Capacitor Placement on Power Supply Board
Figure 5.10: Jumper Placement on Logic Circuit Board
Figure 5.11: Weight-Ratio Jumper Placement
Figure 5.12: Bottom Cover Assembly
Figure 5.13: Assembled DKB-2010 with Bottom Cover Removed
Figure 5.14: Diode Placement in Identifier Matrix ........................................... 44
Figure 6.1: Logic Circuit Board Test Points .................................................... 50
Figure 6.2: Keyswitch Circuit Board Test Points ............................................. 51
Figure 6.3: Power Supply Circuit Board Test Points ....................................... 52

3
ILLUSTRATIONS (continued)
Figure 8.1: DKB-2010 Block Diagram ........................................................... 61
Figure 8.2: Drawing Conventions ................................................................. 62
Figure 8.3: Keyboard Encoder ..................................................................... 63
Figure 8.4: ROM Code Converter and Buffer Control ...................................... 65
Figure 8.5: RTTY Control and Decoder ......................................................... 67
Figure 8.6: Shift Register Control ................................................................. 69
Figure 8.7: RTTY Encoder and Loop Interface ............................................... 71
Figure 8.8: RTTY Timing Chain .................................................................... 73
Figure 8.9: RTTY Character Counter ............................................................ 75
Figure 8.10: Morse Character Generator ........................................................ 77
Figure 8.11: Morse Output Control ................................................................ 79
Figure 8.12: Quick Brown Fox Generator and ID Control ................................. 81
Figure 8.13: Identifier .................................................................................. 83
Figure 8.14: Three-Character Sequencers ...................................................... 85
Figure 8.15: Power Supply Module ................................................................ 87
Figure 8.16: Power Supply Board Component Layout ..................................... 89
Figure 8.17: Keyboard Circuit Board Component Layout ................................. 90
Figure 8.18: Keytop Positions ....................................................................... 91
Figure 8.19: Main Logic Board Component Layout - IC's ................................. 92
Figure 8.20: Main Logic Board Component Layout - Small Parts ...................... 93
TABLES
Table 3.1: Characters Produced by Bracketed Keys ...................................... 13
Table 4.1: RTTY Timing Chain Output Frequencies ....................................... 27
Table 4.2: ASCII Character Codes Used in the DKB-2010 .............................. 36
Table 4.3: ROM Character Input and Output Code ....................................... 37
Table 4.4: RTTY Baudot Codes ................................................................... 38
Table 4.5: Morse Codes ............................................................................. 39
Table 5.1: Coding Chart for Identifier .......................................................... 41
Table 6.1: Test Points - Logic Circuit Board ................................................. 49
Table 6.2: DKB Logic Board Connector (J305) .............................................. 53
Table 6.3: DKB Keyboard Connector (J306) and DKB Power Supply (J307) .... 54
Table 6.4: DKB-2010 Wire List .................................................................... 55
Table 6.5: Integrated Circuit Pin Numbers for Ground And Power .................. 56

4
DKB-2010 SPECIFICATIONS
RTTY MODE
Code:
International Teletype, Baudot
Character Format:
1 start bit (space)
5 data bits (mark or space)
1.5 stop bits (mark)
The duration of each bit is one select time,
determined by the transmission rate. The minimum
stop bit length for Baudot code ranges from 1 to
1.46 bits, depending on transmission rate and
application.
Data Sense:
Mark or "1": holding condition, output con-
ducting.
Space or "0": signaling condition, output noncon-
ducting.
Character Transmission Rates:
60 words per minute, 45.45 baud.
Select time: 22 msec.
66 words per minute, 50.0 baud.
Select time: 20 msec.
75 words per minute, 56.9 baud.
Select time: 17.57 msec.
100 words per minute, 73.7 baud.
Select time: 13.47 msec.
Also available on special order:
132 words per minute, 100 baud
Select time: 10 msec.
Transmission Rate Accuracy:
Crystal controlled to within ± .05 % for ambient
temperatures from 50 to 95 °F (10 to 35 °C).
Output Interface:
Isolated loop switching transistor.
Ratings:
Voltage, nonconducting: 250 V DC
Current, conducting: 80 mA DC
Isolation voltage rating:
Either loop connection to chassis and ground 250
V AC or DC.
Output Power Rating: 1 Watt.
RTTY Keyfunctions:
10 numeric (0 through 9)
26 alphabetic (A through Z)
15 punctuation marks:
. , : ; / " - ! " # & $ () '
3 carriage control keys: linefeed
carriage return, and blank
2 shift keys
1 break key
2 manual case-change keys
2 three-character memory keys (CQ and AUX)
(repeating)
Unless otherwise requested, AUX key transmits
"DX" plus a space.
1 identifier key (HERE IS) (repeating)
1 test message key (QBF: "quick brown fox")
(repeating)
1 space bar
Identifier:
Transmits the letters "DE" followed by the pre-
programmed station call sign of up to 12
characters when the HERE IS key is struck.
Message repeats as long as key is held down.
Test Message Generator:
Transmits the message "THE QUICK BROWN FOX
JUMPS OVER THE LAZY DOG'S BACK
Ø123456789" when the QBF key is struck.
Repeats if key is held down.
End-of-Line Warning:
Panel lamp lights and audio tone burst is emitted
if more than 64 printing characters are trans-
mitted without an intervening carriage return.
Character Buffer Memory:
Stores up to three characters if typing speed
exceeds character transmission rate. Panel lamp
warns when memory is full. Optional 64 and 128
character buffers are available.
N-Key Rollover:
New key may be pressed before the preceding
key is released.
Automatic Case Shift:
Numbers may be transmitted without use of the
shift key; case shift codes are transmitted auto-
matically.

5
DKB-2010 SPECIFICATIONS (continued)
Morse Mode
Code:
International Morse
Data Sense:
Keyed: output conducting
Space: output nonconducting
Character Transmission Rate:
Continuously adjustable from less than 8 to
greater than 60 words per minute.
Character Weight:
Any of six weight ratios from 1:7 to 3:1 may be
chosen. A panel switch permits selection of the
four standard weights: Heavy (5:3), normal
(1:1), light (3:5), and very light (1:7). The switch
wiring may be altered to substitute ratios of 1:3
and 3:1 in place of one or two of the standard
weights.
Note: Character weight is the ratio of dot
duration to the length of the space between
adjacent dots or dashes. For the normal weight
ratio of 1:1, the ratio of dot and dash lengths is
1:3. For other weights, dash duration is equal to
the length of two dots plus the duration of one
space between consecutive dots or dashes.
Output Interface:
Transmitter keying transistor may be used for
either cathode or gridblock keying (but not both
simultaneously).
Transistor ratings:
Cathode keying:
Voltage, nonconducting:
+250 V DC
Current, conducting: 150 mA DC
Grid-block keying:
Voltage, nonconducting:
–150 V DC
Current, conducting: –150 mA DC
Output power rating: 1 Watt
Morse Keyfunctions:
10 numeric (0 through 9)
26 alphabetic (A through Z)
9 punctuation marks:
. , : ; / " - ' ()
5 special character keys:
(SK, AS, AR, KN, BT)
2 shift keys
1 break (tune) key
1 error key (8 dots)
2 three-character memory keys:
(CQ and AUX)
1 identifier key (HERE IS)
1 space bar
All RTTY-only keys produce the Morse error signal.
Sidetone Oscillator:
Internal speaker emits audio tone keyed in
synchronism with output keying transistor.
Volume adjustable by panel control. Pitch
adjustable by internal control.
Identifier:
Performs same function as in RTTY mode.
Character Buffer Memory:
Performs same function as in RTTY mode.
N-Key Rollover:
Performs same function as in RTTY mode.
General:
Size: 13.5" wide, 5" high, 9" deep
(34.3 × 12.7 × 22.9 cm)
Weight: 5 lbs. (2.27 kg.)
Power:
105 - 125 V AC, 47 to 440 Hz, 1/8 amp. (Optional
220 - 250 V AC, 1/16 amp).
Operating Temperature:
50 to 95 °F (10 to 35 °C).

6
I. GENERAL INFORMATION
1.1 Description
The HAL DKB-2010 is a solid-state, electronic keyboard designed for transmitting both RTTY (Baudot)
and Morse codes. A successor to HAL Communication's popular first-generation keyboards, the DKB-2010
provides many advanced operating features:
1. A three-character buffer memory stores the characters typed for transmission at a constant rate.
Coupled with the n-key rollover capability, it helps iron out variations in typing speed and style.
2. A station identifier, included as standard equipment, automatically transmits the station call sign at the
touch of a key.
3. The four RTTY operating speeds (60, 66, 75, and 100 words per minute) are switch selectable and, to
assure stability, crystal controlled. The Morse speed is continuously variable from 8 to 60 words per
minute.
4. A warning light and tone signal the RTTY operator when line length exceeds 64 characters.
5. A built-in RTTY test generator automatically transmits a standard test message ("THE QUICK BROWN
FOX JUMPS OVER THE LAZY DOG'S BACK Ø123456789") at a single keystroke.
6. The Morse code weight can be set to any of four ratios by a frontpanel switch. Weight is unaffected by
changes in speed.
7. The space bar functions in the Morse mode to simplify interword spacing.
8. Two "memory" keys can be preprogrammed to automatically transmit three-letter combinations. One is
normally used to transmit "CQ", followed by a space. The code for the other (the AUX key) is selected
by the owner at the time of purchase; if not specified it is coded to transmit "DX" followed by a space.
For the RTTY operator, the DKB-2010 provides automatic transmission of the case-shift code when
typing numbers and letters; the shift key is needed only for certain punctuation marks. The loop switching
transistor in the keyboard output stage is completely isolated from chassis and ground so that it may be
connected at any convenient point in the station loop circuit.
For Morse operation, a sidetone oscillator with adjustable pitch and volume simplifies monitoring of the
transmitted code. Five double-character keys (SK, AS, AR, KN, and BT), along with an error key (which
transmits eight dots), provide the special characters needed in Morse work. A tune key overrides the
keyboard output and keys the transmitter on for adjustment. Keying is accomplished by a high-voltage
switching transistor, which may be connected for either cathode or grid-block keying.
The keyboard circuitry is constructed on three G-10 glass-epoxy circuit boards, housed in an attractive
yet rugged two-tone gray cabinet. The circuit boards are interconnected by a factory-prepared wiring
harness to simplify construction and servicing. Output connections are conveniently located on the rear
panel. The internal power supply incorporates active, series-pass regulators to ensure stability.
1.2 Instrument Identification
Your keyboard is identified by a serial number tag on the rear panel. It is suggested that you record it in
the space provided on the title page of this manual. Please refer to the serial number when contacting the
factory for information or service.

7
1.3 Accessories Furnished
The DKB-2010 is shipped with the following accessories:
2 6-contact plugs
2 3-contact plugs
18 female connector pins
1 phono plug
2 lengths, 2 conductor shielded cable
1 operating and service manual
1.4 Manual Preview
This manual is provided to help you get the most from your keyboard, whether you have selected the
factory-wired or the kit model. In the following sections, you will find instructions for installing and operating
the DKB-2010. Please read them carefully before attempting to use your keyboard.
Section 4 provides a full description of the keyboard circuitry. Step-by-step instructions for constructing
the keyboard kit will be found in Section 5; testing and maintenance are covered in Section 6. Parts lists and
a complete set of schematic diagrams are bound at the rear of the manual in Sections 7 and 8 for ease of
reference.
FOR KIT-BUILDING INSTRUCTIONS, TURN TO PAGE 5-1.

8
II. INSTALLATION
2.1 Initial Inspection
When you unpack your DKB-2010 keyboard, examine it carefully. If evidence of shipping damage is
found, contact the carrier immediately. Before discarding the packing material, check that all parts and
accessories are accounted for (included accessories are listed in Section 1.3). If any are missing, please
notify the factory in writing.
If your keyboard is in kit form, check the parts against the list in Section 7 of this manual. Then turn to
Section 5 for assembly instructions.
2.2 Preliminary Checkout
Connect the power cord to an AC source of the proper voltage and frequency.
NOTE: The keyboard can be connected for either 105 to 125 volt or 210 to 250 volt operation. Factory-
assembled units are wired for nominal 115 volt input unless otherwise indicated by a tag attached to
the power cord. Before connecting the power cord, be certain that the voltage of the outlet
corresponds to the keyboard input voltage rating.
To ensure operator safety, connect the power cord to a three-prong outlet with safety ground. DO NOT
attempt to defeat the grounding prong of the keyboard cordset. To do so will void the warranty.
Next, rotate the mode switch to the Morse position. Switch the keyboard on by rotating the volume
control clockwise to about the center of its range. When power is first applied, the identifier and the three-
character memory circuits may be in their active states. If so, the stored characters will be clocked out of
the memory in rapid succession. Wait until the process is complete. Then press any of the letter or number
keys. The keyboard should produce a keyed audio tone corresponding to the Morse code pattern of dots and
dashes for the character. Test several other keys, adjusting the speed, volume, and weight controls to check
their operation. If this preliminary test is satisfactory, the keyboard is ready to be connected to your CW
transmitter and RTTY loop circuit.
If the keyboard will be used for both RTTY and Morse operation in your station, prepare the connecting
cables described in Sections 2.3 and 2.4. The keyboard may be left connected to both the RTTY loop and
the CW transmitter; it is not necessary to exchange cables or remove plugs when changing modes, as the
RTTY and Morse output stages of the keyboard are completely independent. Of course, the keyboard need
not be used for both modes. In that case, simply prepare cables for the appropriate output Jacks and leave
the others unconnected.
BEFORE PROCEEDING WITH THE INSTALLATION, DISCONNECT THE AC POWER CORD.
2.3 CW Transmitter Keying Connections
The keyboard Morse output stage is a high-voltage switching transistor. When connected to the
transmitter, this electronic switch takes the place of the normal hand key. The keyboard may be connected
for either cathode or grid-block keying (but not both at the same time), depending on which of the two
rear-panel keying jacks is used. The two Morse output connections may not be used at the same time. The
Morse output control circuitry is shown in Figure No. 8.11.
Before attempting to connect the keyboard to the transmitter keying terminals, examine the transmitter
circuit diagram carefully to determine the keying method used. The keyboard cannot be used with "floating"
key circuits; one of the two keying terminals must be grounded within the transmitter.
The transistor keying switch is rated to withstand 250 volts at up to 150 mA in cathode keying service.
For grid-block keying, the voltage at the key should not exceed -150 volts, and the current should not be
greater than 150 mA. Before connecting the keyboard, measure the voltage across the keying terminals of
the transmitter with the key open and the current through the key when it is closed to ensure that these
ratings are not exceeded.

9
Some transmitters (such as the Yaesu FTDX-560 and several of the Swan transceivers) include a wave-
shaping filter in the key line, with a capacitor connected directly across the key terminals. The charge stored
in this capacitor can produce a current surge large enough to damage the keyboard switching transistor
when the transmitter is keyed. If such a capacitor is present in your transmitter, a resistance of between
100 and 390 ohms must be inserted in series with the line to the keyboard. Use a ½ Watt resistor, choosing
the highest value in this range that does not degrade transmitter performance. The resistor can be mounted
on the plug used to connect to the keyboard output jack.
CAUTION: HIGH VOLTAGES MAY BE PRESENT AT THE TRANSMITTER KEYING TERMINALS.
UNPLUG THE TRANSMITTER AND THE KEYBOARD BEFORE MAKING THE FOLLOWING CONNECTIONS.
For cathode keying, the keyboard output switch is connected in series with the cathode circuit of the
keyed transmitter stage. A typical installation is illustrated in Figure 2.1. Use a length of shielded wire to
connect from the transmitter to the keyboard Morse Output jack. Hook the center conductor to the cathode
of the keyed stage. Ground the shield at the transmitter. Install a plug on the other end of the cable,
connecting the center conductor to pin 3 and the shield braid to pin 2. Connect a jumper wire between pins
1 and 3 of the plug. Prepare the plug connections as shown in Figure 2.4A. Insert the plug into the Morse
Output jack on the rear panel of the keyboard.
A typical arrangement for grid-block keying is shown in Figure 2.2. In this circuit, the transistor switch
shorts the negative grid blocking voltage to ground when the transmitter is to be keyed. As in the case of
cathode keying, a shielded cable should be used to interconnect the transmitter and keyboard. At the
transmitter end, connect the center conductor to the normal keying point in the bias circuit. Ground the
shield. At the other end of the cable, install a plug with the center conductor of the cable connected to pin 1
and the shield to pin 2. Connect a jumper between pins 2 and 3 of the plug. Prepare the plug connections
as shown in Figure 2.4A. Insert the plug into the Morse output jack on the rear panel of the keyboard.
CAUTION: POTENTIALLY LETHAL VOLTAGES MAY BE PRESENT AT THE PLUG CONTACTS WHEN THE
TRANSMITTER IS TURNED ON. DO NOT DISCONNECT THE KEYING CABLE FROM THE
KEYBOARD WITHOUT FIRST SWITCHING THE TRANSMITTER OFF.
Once the keying cable has been prepared and the plug inserted into the proper keyboard jack, set the
mode switch to Morse and switch the keyboard on. Allow time for the identifier memory to clear itself; then
press any of the letter or number keys. The audio sidetone oscillator should produce the correct sequence of
dots and dashes for the character, and the transmitter should key simultaneously.

10
2.4 RTTY Loop Connections
Since the RTTY output stage of the keyboard is isolated from ground and from the chassis, the keyboard
can be connected at any convenient point in the station loop circuit, provided that the voltage from either
loop connection to ground does not exceed 250 volts. Loop current is switched by a transistor, rated to carry
up to 80 mA DC and to withstand loop voltages up to 250 volts DC. Before making any connections to the
keyboard, measure the loop voltage in the space condition and the current during mark pulses to make
certain that neither exceeds the keyboard ratings.
UNPLUG THE KEYBOARD AND THE STATION LOOP SUPPLY BEFORE TAKING ANY
CONNECTIONS.
A typical station loop circuit is shown in Figure 2.3. A 6 pin plug is used to connect the loop to the
keyboard. Break the loop circuit at the desired point and connect the positive lead to pin 1 of the plug.
Connect the negative lead to pin 3. The cable shield, if one is used, may be connected to pin 2. A jumper
(or additional RTTY equipment) should be connected between pins 4 and 6. Double check the polarity of the
loop leads, as reverse voltages may damage the switching transistor. Then insert the plug into the RTTY
LOOP jack on the keyboard rear panel.
If the negative loop keying lead is grounded, the connections shown in Figure 2.4 should be used.
Prepare the plug connections as shown in Figure 2.4A.

11
The diode bridge circuit shown in Figure 2.5, if installed at the RTTY LOOP plug, makes it possible to
connect the loop leads without regard for polarity. Diode polarity must be carefully observed when
constructing the circuit, and the leads must be properly insulated and positioned so that they do not short
together. This circuit is not recommended for loops operating at less than 30 volts, as the diodes may
introduce too much voltage drop. The bridge arrangement may be used even if one lead of the loop circuit
is grounded.

12
CAUTION: LOOP SUPPLY VOLTAGES ARE EXPOSED AT THE CONTACTS ON THE PLUG. IF YOU USE A HIGH
VOLTAGE LOOP SUPPLY, DO NOT SWITCH IT ON UNLESS THE PLUG IS INSERTED INTO THE
KEYBOARD RTTY LOOP JACK.
Once the connections have been made and the plug inserted, the loop supply and keyboard may be
plugged in and switched on. With a printer or visual display unit connected into the circuit, set the mode
switch to the correct speed and press any of the character keys. The printer should reproduce the character.
If the printer is in letters case, pressing a letter key followed by a number key should shift it to figures case.
Typing another letter should return it to letters case. After 64 printing characters have been typed without
an intervening carriage return, the END OF LINE lamp will light and the speaker will emit an audio tone
burst.
2.5 Audio Output Connections
The audio signal from the sidetone oscillator may be coupled to an external circuit via the AUDIO OUT
jack. Solder the center conductor of a shielded cable to the pin of a phone plug, and connect the braid to
the plug shell. Insert the plug into the output jack. The amplitude of the audio signal may be adjusted with
the keyboard volume control.

13
III. OPERATING YOUR KEYBOARD
3.1 Introduction
The many advanced features of the DKB-2010 keyboard make it easy to produce flawless RTTY and
Morse code signals. The operating tips presented in this section will help you take full advantage of your
keyboard's capabilities, RTTY operation will be covered first. Since most features are operative in both
modes, Morse operation is very similar. The few differences are explained in Section 2.3. Figure 3.1 shows
the position of the keys and controls.
3.2 RTTY Operation
Switch the keyboard on by rotating the volume control clockwise to about the middle of its range. The
quick brown fox and identifier circuits may be active when power is applied. If so, they will complete their
sequences and clear themselves in ten seconds or less. Since it is possible for both circuits to start in the
active state, the output during this period may be unintelligible. When the sequence is complete, set the
mode control to the desired RTTY operating speed, and turn on the station loop supply and printer.
To transmit any character, simply press the corresponding key. It is not necessary to depress one of the
SHIFT keys before typing numbers, as the keyboard will produce the required figures-case code
automatically before transmitting the number. Likewise, the next time you strike one of the letter keys, the
letters-case code will be sent. The most common punctuation marks (period, comma, colon, semicolon, and
fraction bar) can also be typed without using the SHIFT key.
Some punctuation marks appear on the upper half of their keytops. To type these characters, press
either of the two SHIFT keys and hold it down white you strike the desired key. Then release the SHIFT key.
Five of the keys are inscribed with two characters joined by brackets. The characters these keys produce
change when the keyboard is switched from RTTY to Morse operation. The keys and their functions are
listed in Table 3.1.
In the RTTY mode, the character shown on the lower half of the key is transmitted if neither of the
SHIFT keys is depressed when the character key is struck. If, on the other hand, a SHIFT key is held down
while the colon key is struck, the bell code will be transmitted. The hyphen and semicolon keys produce
blanks in the shifted mode, The carriage return and linefeed keys transmit the same character regardless of
the shift key position.
Unless you are a very proficient typist, you probably will not be able to type characters faster than the
keyboard can transmit them. If you type in short, rapid bursts, however, you may find that you can
momentarily "get ahead" of the keyboard – that is, you may strike a new key before the code for the
preceding one has been transmitted in its entirety. The three-character buffer memory and n-key rollover
features of the DKB-2010 help to compensate for these typing speed variations.
Table 3.1: Characters Produced by Bracketed Keys
Key
RTTY Mode
Morse Mode
Unshifted
Shifted
Unshifted
Shifted
Bell
:
Colon
Bell
__
SK
Colon
AS
-
Hyphen
Blank
__
AS
Hyphen
BT
;
Semicolon
Blank
__
BT
Semicolon
AR
LF
Line
Feed
Line
Feed
__
AR
__
AR
KN
RETURN
Carriage
Return
Carriage
Return
__
KN
__
KN

14
Figure 3.1 Location of Controls and Keys
As soon as you type the first character of a series, the keyboard will begin transmitting it. You may then
type two more characters, even though transmission of the first one has not been completed. The keyboard
will "remember" characters and transmit them in the proper sequence. To help you pace your typing, the
MEMORY FULL lamp will light when three characters have been stored. Simply wait until the light goes out,
indicating that there is room for another character in the memory, before your next keystroke. If you should
happen to press another key while the memory light is on, the last character in the memory will be replaced
with the new one typed.
The n-key rollover feature means that you do not have to release a key before striking the next one. The
keyboard will transmit the characters in the proper order.
Another operating convenience of the keyboard is the Line length indicator. If you type more than 64
consecutive printing characters, the END OF LINE lamp will light and an audio tone will be emitted as a
reminder to send a carriage return and linefeed. Non-printing characters, such as Linefeeds and blanks, are
not counted as part of the 64 characters, This warning feature is particularly useful when you are punching
paper tape.
Five standard RTTY control keys are provided. The LINEFEED, RETURN (carriage return), and BLANK
keys perform their normal functions of advancing the printer paper one line, returning the carriage to the
left margin, and punching blank characters on paper tape, respectively. Although the keyboard produces all
required figures-case and letters-case codes automatically, a figures (FIGS) key and letters (LTRS) key are
provided so that you may manually shift the case of the receiving teleprinter. It is not necessary to use
these keys when transmitting characters which appear on the upper half of the keytops. Instead, use one of
the SHIFT keys as described previously. The keyboard will automatically transmit the figures-case code, and
will also return the printer to letters case the next time a letter key is struck.
The keyboard includes a number of special keys which simplify RTTY operation by automatically
transmitting strings of several characters at a single keystroke. The key labeled QBF produces the standard
RTTY test signal: "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG'S BACK Ø123456789". It is not
necessary to hold the key down once the message has started. If, however, the key is held down through
the end of the sequence, the entire message will be repeated.
A station identifier, actuated by the HERE IS key, is preprogrammed to transmit the letters "DE", followed
by your station call sign. The sequence will be repeated as long as the key is held down.
The CQ key produces the letters "CQ" followed by a space. Another special key, labeled AUX (for
auxiliary) can be preprogrammed to transmit any group of three characters. On factory-assembled
keyboards, this key is programmed with the characters requested by the purchaser when the keyboard was
ordered. If not specified, it is programmed to produce the letters "DX" followed by a space. Kit builders may
select the characters at the time of construction. Both keys repeat their character sequence if held down.

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The last of the special keys is the BREAK key. In its idling state (when no characters are being
transmitted), the keyboard loop switching transistor conducts. Hence, the loop circuit is in the mark
condition. For testing, the current may be interrupted, changing the loop to the space condition, by
depressing the BREAK key. Releasing the key returns the loop switch to normal operation.
When the keyboard power switch is turned off, the station loop will be interrupted, since no current can
flow in the loop switching transistor. If you wish to use other equipment connected in the loop, the circuit
may be completed by either switching the keyboard on and allowing it to idle, or by setting the MODE switch
to the Morse position. In the latter case, one section of the MODE switch bridges across the output
transistor, allowing loop current to flow.
3.3 Morse Code Operation
Morse codetyping with the DKB-2010 keyboard is very similar to RTTY operation. Set the MODE switch to
the Morse position and rotate the volume control clockwise to switch the keyboard on. Allow a few seconds
for the identifier circuit to clear itself. Set the WEIGHT control to Norm. Touch any letter key and adjust the
VOLUME control for the desired audio sidetone level. The SPEED control may be adjusted for any code
speed from 8 to 60 words per minute.
The MEMORY FULL lamp and the n-key rollover features work the same as in the RTTY mode to help you
pace your typing. Since Morse transmissions do not involved a fixed line length, the END OF LINE warning
light is not operative. However, it may light if the MODE switch is set to the Morse position when the
keyboard power is switched on. To extinguish the lamp, move the MODE switch to any of the RTTY
positions and press the return key. Then return the switch to the Morse setting.
The HERE IS, CQ, and AUX keys operate in their normal manner, but the RTTY test generator (QBF key)
is inappropriate for Morse transmission and therefore does not function. The BLANK key produces the
standard eight-dot Morse error signal.
Five "double character" keys ([SK], [AS], [AR], [KN] and [BT]) are available exclusively in the Morse
mode. Each of these appears on the upper portion of the key, but is enclosed by square brackets indicating
that it is not necessary to press a SHIFT key when transmitting the character. If, however, you strike the SK,
AS or BT keys while holding one of the shift keys down, the punctuation marks shown on the lower half of
the key will be produced, as shown in Table 3.1. The AR and KN keys produce the same output regardless
of the SHIFT key position.
Only 10 of the punctuation marks are used for Morse code ( . , / : ; ? - ( ) and '). Of these, the last seven
are transmitted using the SHIFT key. Attempting to transmit any of the remaining punctuation marks
produces the Morse error signal
The space bar performs its normal function to ensure proper spacing between words. You will find it
particularly useful when you type fast enough to store more than one character at a time in the keyboard
memory.
The BREAK key operates in the Morse mode, but has a different effect than in RTTY operation. When
pressed, it closes the electronic keying switch, holding the transmitter on the air for tuning and adjustment.
Releasing the key returns the keying circuit to normal operation.
The WEIGHT control offers a choice of four weight ratios, varying from very light (1:7) to heavy (5:3). In
Morse code, the Weight is the ratio of the length of a dot to the length of the space between dots and
dashes. At the very light setting, the dots will sound very short. As the switch is moved toward the heavier
weight ratios, the dots will sound longer when compared to the spaces between dots and dashes.
Experiment with the setting until you find the one that seems the most pleasing.
The volume control adjusts the sidetone oscillator output level. The pitch may be changed, if necessary,
by an internal adjustment, described in Section VI.

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IV. THEORY OF OPERATION
4.1 Introduction
This section describes the circuitry of the DKB-2010 keyboard system and explains its operation, first in
general terms and then in detail.
A block diagram of the system is provided in Figure 8.1, bound in Section 8 with the schematic diagrams
of the keyboard circuitry. The drawing symbols and conventions used are illustrated in Figure 8.2.
The keyboard uses integrated digital logic circuitry throughout. Readers unfamiliar with the principles of
logic circuits may find it helpful to refer to an introductory discussion of The subject before proceeding 1.
4.2 General Operating Principles
The primary function of the keyboard circuits is to convert the closure of a keyswitch into a series of
sequential pulses-marks and spaces in the RTTY mode, or dots and dashes in the Morse mode. These pulses
appear at the keyboard output stages, where they activate switching transistors to key the station loop
circuit or CW transmitter.
Of the 53 independent keyswitches, 46 are arranged in a matrix. The remaining seven are used for
special functions. The 46 matrix keys are connected to a large-scale integrated-circuit keyencoder.
Whenever this circuit senses closure of a keyswitch, it produces a seven-bit digital code, which appears in
parallel form at the circuit's output. This code is the ASCII equivalent 2 of the character to be transmitted.
Some of the keyswitches can produce two different characters. One of these characters is printed on the
lower half of the keytop. Those appearing on the upper half are "shifted" characters, transmitted by
pressing one of the shift keys along with the character key. Closure of the shift keyswitch instructs the
keyencoder to produce the ASCII code for the shifted rather than the unshifted character.
Of the seven keys not connected to the matrix, two are the shift keys just mentioned. Four others are
used to initiate special character sequences: the station identifier message, the "quick brown fox" test
signal, and the special three-character memory sequences. The remaining key, labeled BREAK, allows the
operator to break the RTTY loop manually, or, in the Morse mode, to key the transmitter manually for
tuning.
The ASCII code produced by the keyencoder or one of the special message generators must be
converted to a different pattern of bits to produce the RTTY or Morse code pulse sequence. The conversion
is accomplished by a read only memory (ROM) preprogrammed with the code patterns required for each
character. The seven-bit code from the keyencoder or the special message generators, along with an eighth
bit which selects the RTTY or Morse mode, is applied to the eight address inputs of the ROM. The input code
addresses a particular eight-bit location in the memory. In that location is stored the correct code for the
character, which appears at the ROM output. Thus the ASCII code is converted to the Morse or RTTY bit
pattern.
The ROM output is fed to an eight-bit buffer memory. If the keyboard is idle, the code is passed directly
to the 10-bit static shift register. If the latter register already contains a character, however, the buffer
stores the code until the shift register is cleared and ready to accept new input data.
Up to this point, all character codes are handled in parallel format (all bits are transmitted simultaneously
on parallel lines). Both the Morse and RTTY transmission modes, however, require that the output pulses
appear sequentially. The 10-bit shift register performs the necessary parallel-to-serial conversion. The input
code bits from the storage buffer are loaded into the shift register in parallel. Clock pulses are then applied
to the register, causing the bits to appear in sequence at the register output.
1One useful reference is the text by Thomas P. Sifferlen and Vartan Vartanian, Digital Electronics with Engineering
Applications (Englewood Cliffs, N. J.: Prentice Hall, Inc., 1970).
2 The ASCII code is the American Standard Code for Information Interchange, widely used in data processing systems.
Table 4.2 in Section 4 lists the ASCII code for each character used in the DKB-2010 keyboard.

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Depending on the setting of the mode switch, the register output activates either the Morse character
generator or the RTTY loop switching circuit. In the RTTY mode, the output code keys the loop switch
through an isolation circuit. For Morse transmission, the bits must be converted to pulses of unequal length,
forming dots and dashes. The Morse character generator accepts the serial code from the shift register and
performs the conversion. The generator output activates the Morse keying transistor and the sidetone
oscillator.
Several additional circuits are included to increase operating convenience. In the RTTY mode, a counter
keeps track of the number of characters transmitted after a carriage return. It activates the RTTY END OF
LINE lamp and triggers a toneburst from the sidetone oscillator when 64 characters have been produced.
The "quick brown fox" generator produces the standard RTTY test message when the QBF key is
pressed. A similar automatic character sequencer, usable in both the RTTY and Morse modes, produces the
letters DE and the station call sign whenever the operator strikes the HERE IS key. Two other automatic
sequencers produce three-character groups at a single keystroke. One is normally coded to transmit the
letters CQ followed by a space. The other, activated by the AUX key, may be programmed for any group of
three characters of the user's choice by rearranging diodes in a memory matrix. All of the sequencers will
repeat their messages as long as the activating keyswitch is held down.
4.3 Circuit Analysis
In the following sections, the keyboard circuitry will be described in greater detail. In the course of the
discussion, frequent reference is made to the schematic diagrams included in Section 8. Figure 8.2, which
precedes the schematics, illustrates the drawing conventions used.
To aid in tracing signal paths through the keyboard circuit diagrams, each line which connects between
portions of the circuit shown on different drawings is designated by a name that describes its function (e.g.,
BUFFER FULL). Some of the labels are overscored, indicating that the signal carried by the line is inverted or
"negative true". Thus the BUFFER FULL line is at its "high" level (above 2,4 Volt) when a character has been
stored in the buffer register. On the other hand, the line designated RTTY TONE activates the tone
generator when it changes to its "low" state (less than 0.8 Volt).
To aid in locating the source of the signals on these lines, a code is included with the name, except, of
course, at the point where the signal originates. The code consists of a number and a dash, followed by a
letter and number pair (for example, 8.1-B3). The first number indicates the figure in which the signal
source may be found – in this case Figure 8.1. Each schematic diagram includes coordinates, similar to
those used on maps, along two of its edges, The letter-number pair of the code gives the coordinates of the
area on the drawing where the signal originates. In the case of the code 8.1-B3, the signal source may be
found in Section B3 of Figure 8.1.
Two signal lines which deserve special attention are the M/R line and its inverted counterpart, the M/R
line. The signal on these buses switches the keyboard between the Morse and the RTTY mode, disabling the
RTTY circuits when the mode switch is set to the Morse position, and the Morse circuits when it is set to one
of the RTTY operating speeds, the M/R bus is high in the Morse mode and low in the RTTY mode; the M/R
line assumes the opposite states.
Most of the keyboard circuit components and wiring are contained on two printed circuit boards. The
boards are interconnected by a wiring harness with a card-edge connector at each end. The harness also
connects to the cabinet-mounted components and to the power supply. Small squares containing a single
letter or number appear on some signal lines to indicate that the line is connected to the harness through
one of the edge connectors. The number or letter in the square corresponds to the connector pin
designation.
The keyboard encoder is included on the circuit board to which the key-switches are mounted. All other
circuitry, except for cabinet mounted parts, is found on the other boards. A wire list of the harness
connections is included at the end of Section 8.

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