Hal Communications ST-6000 User manual

ST-6000
FSK
DEMODULATOR

HAL ST-6000 FSK DEMODULATOR / KEYER
Technical Manual
********************************************************************************
Copyright © 1976 by HAL Communications Corp., Urbana, Illinois.
February, 1982 Printing
Reprint January, 2019, DC7XJ

HAL ST-6000 DEMODULATOR
CONTENTS
1. INTRODUCTION 1-1
2. SPECIFICATIONS 2-1
3. INSTALLATION 3-1
3.1 Initial Inspection 3-1
3.2 Use of Factory Supplied Cables 3-1
3.2.1 Audio Input Connection 3-1
3.2.2 Audio Output Connection 3-2
3.2.3 Loop 1 Cable Connection 3-2
3.2.4 Motor Power Connection 3-2
3.2.5 KOS Cable Connection 3-7
3.2.6 Separate Keyboard Connection 3-10
3.2.7 RS-232C Cable Connection 3-10
3.2.8 CW-ID Key Cable Connection 3-10
3.2.9 AC Power Cord Connection 3-10
3.2.10 Ground Connection 3-10
3.3 Alternate Connection to the ST-6000 3-11
3.3.1 Use of External Loop Supplies and Multiple Loop Circuits 3-12
3.3.2 Separate Printer and Keyboard Connection 3-12
3.3.3 Full Duplex Operation of the ST-6000 3-12
3.3.4 External Data Processing Equipment 3-15
3.3.5 External Oscilloscope Connections 3-15
3.3.6 Tone Keyer Control Connections 3-15
4. OPERATION 4-1
4.1 Front Panel Controls and Indicators 4-1
4.2 Simplified Operating Procedure 4-2
4.3 Reception of Radio Teleprinter Signals 4-2
4.3.1 Receiver for FSK Reception 4-3
4.3.2 Receiver for AFSK Reception 4-4
4.3.3 Tuning a RTTY Signal 4-4
4.4 Use of the ATC Circuit 4-5
4.5 Use of the DTH Circuit 4-5
4.6 Use of the Limiter Switch - FM vs. AM 4-6
4.7 Use of the SENSE Switch 4-6
4.8 Use of the PRINT Switch 4-6
4.9 The KOS Circuit 4-7
4.10 Use of the Autostart Circuitry 4-7
4.11 Antispace Circuitry 4-8
4.12 Tone Keyer Circuit 4-8
4.13 Transmitting Radio Teleprinter Signals 4-9
4.13.1 Transmitting FSK Signals 4-9
4.13.2 Transmitting AFSK Signals 4-11
4.13.3 Adjustment of the ST-6000 Tone Keyer 4-11

5. ST-6000 CIRCUIT DESCRIPTION 5-1
5.1 ST-6000 Analog Processing Circuits - Input Circuit Board 5-1
5.1.1 Input AGC Circuit 5-1
5.1.2 Input Bandpass Filters 5-1
5.1.3 Limiter Amplifier 5-1
5.1.4 Discriminator Filters 5-2
5.1.5 Discriminator Detectors 5-2
5.1.6 A/S Amplifier and Detectors 5-2
5.1.7 Active Lowpass Filter 5-2
5.1.8 ATC Circuit 5-2
5.1.9 Tone Keyer 5-3
5.2 ST-6000 Control Circuit Board 5-3
5.2.1 Slicer and DTH Circuits 5-3
5.2.2 Antispace Circuit 5-4
5.2.3 Pre-autostart Data Output 5-4
5.2.4 Autostart Circuit 5-4
5.2.5 Standby Circuit 5-4
5.2.6 Post-autostart Data Output 5-5
5.2.7 Loop Keyer Stages 5-5
5.2.8 RS-232/MIL-188 Interfaces 5-6
5.2.9 KOS Circuit 5-6
5.3 Front Panel Indicators 5-6
5.4 Power Supply 5-7
5.5 Oscilloscope 5-7
5.6 Cabinet Wiring 5-8
5.7 User Servicing 5-8
5.8 Troubleshooting Guide 5-9
APPENDIX A: RF-Induced Problems 6-1
TABLES
Table 4.1 ST-6000 Front Panel Controls 4-1
Table 4.2 ST-6000 Front Panel Indicators 4-2
ILLUSTRATIONS
Figure 3.1 "Standard" Cable Connections to the ST-6000 3-3
Figure 3.2 Loop Connections to the ST-6000 3-8
Figure 3.3 RS-232 I/O Connections to the ST-6000 3-9
Figure 3.4 Preparation of the ST-6000 Connectors 3-11
Figure 3.5 Alternate Loop Connections 3-13
Figure 3.6 Connections for Full-Duplex Operation 3-14
Figure 3.7 Connections to External Data Processing Devices 3-16

Figure 5.1 ST-6000 Block Diagram 5-11
Figure 5.2 ST-6000 Schematic Diagram Conventions 5-12
Figure 5.3 Input AGC Circuit 5-13
Figure 5.4 Input Bandpass Filter 5-14
Figure 5.5 Limiter Amplifier 5-15
Figure 5.6 Discriminator Filters 5-16
Figure 5.7 Discriminator, Meter Amp., Lowpass Filter, ATC 5-17
Figure 5.8 Tone Keyer 5-18
Figure 5.9 Slicer, Antispace, Autostart 5-19
Figure 5.10 Loop Drivers, Loop Sense 5-20
Figure 5.11 RS-232/MIL-188 Interface 5-21
Figure 5.12 KOS Circuit 5-22
Figure 5.13 Power Supply 5-23
Figure 5.14 Oscilloscope 5-24
Figure 5.15 Input Circuit Board Layout 5-25
Figure 5.16 Control Circuit Board Layout 5-26
Figure 5.17 Oscilloscope Circuit Board Layout 5-37
Figure 5.18 Circuit Board Interconnections 5-28

1-1
1. INTRODUCTION
The Hal Communications Model ST-6000 is a high performance FSK demodulator and tone key-
er designed for use with radio teleprinter systems. The ST-6000 incorporates the features and per-
formance characteristics of previous HAL demodulators as well as offering some features previous-
ly not available.
The ST-6000 is an audio tone type of demodulator and keyer. Audio tones from the receiver,
representing the "mark" and "space" teleprinter code states, are converted into keying pulses by
the demodulator section. Active input and discriminator filters are used in the ST-6000 so that a
wide range of input frequencies can be accommodated. Two standard audio tone sets are normally
stocked by the factory and special tone sets within the 1200 ... 3000 Hz frequency range are avail-
able on special order. The standard tone sets are based on a mark frequency of 1275 Hz ("low-
tone" set) or a mark frequency of 2125 Hz ("high-tone" set) for frequency shifts of 170 Hz, 425
Hz, and 850 Hz. The tone keyer section of the ST-6000 generates the same set of tones for trans-
mitting in addition to a narrow-shift tone for Morse code identification.
The demodulator uses a pre-filter AGC system, an active bandpass filter, a high gain, wide
bandwidth limiter, and active detector circuits. This combination gives outstanding performance for
a wide range of input signal amplitudes even in the face of strong interfering signals. The limiter
stage gain can be reduced for non-limiting operation ("AM"). The pre-filter AGC and active detec-
tors also assure improved non-limiting performance when compared to previous demodulators. A
three pole active lowpass filter follows the detector stages to reduce the post-detection noise
bandwidth.
An Automatic Threshold Correction (ATC) circuit can be switched into the signal chain to provide
correction for bias distortion generated by the propagation path. This feature can also be defeated
with a front panel switch if desired. A Decision Threshold Hysteresis (DTH) circuit can also be
switch selected to provide correction for multi-path propagation distortion of the teleprinter signal.
CMOS digital circuitry is used to provide the automatic printer and motor control as well as the
antispace feature. The ST-6000 autostart circuit senses the presence (or absence) of a valid tele-
printer signal. If the input signal is not recognized as a teleprinter signal, the printer is held in the
"mark-hold" condition. If more than twenty seconds pass without recognition of a valid signal, the
power to the printer motor is removed. The response time of the autostart circuit is switch selecta-
ble to allow "FAST" (1.5 sec.) or "SLOW" (3.5 sec.) response. An antispace circuit is also included
in the digital control section that limits the duration of a space signal to 250 ms or less, preventing
the "running-open" machine condition on continuous space tones.
As mentioned earlier, the tone keyer section generates the same tone set as is used in the de-
modulator section to assure true "transceive" conditions. The tone keyer will also generate an ad-
ditional narrow-shift tone that can be connected to an external keyer circuit for Morse code identi-
fication. All tones of the tone keyer are derived from high frequency crystal controlled oscillators.
The output signal is a low distortion sine-wave generated in a digital-to-analog converter and then
filtered in an active low-pass filter. A wide range of output amplitude (into 500 Ohms) it available
from the ST-6000, adjustable with an internal control. Unlike previous demodulators, the tone key-
er data input circuit is not internally connected to the demodulator but is available on a rear panel
connector. Thus, separate transmit and receive circuits (full-duplex) can be accommodated by the
ST-6000. Conversely, with appropriate rear-panel jumpers, the tone keyer can be connected to the
demodulator for a common transmit/receive circuit (half-duplex) as was the case for the ST-6 de-
modulator. However, the shift of the tone keyer is controlled by the front panel SHIFT switches. Al-
so, the SENSE switch (NORM - REV) controls both the tone keyer as well as the demodulator.

1-2
The ST-6000 input and output circuits have been designed to allow a maximum of user flexibili-
ty. Many signal and control lines have been brought-out to rear panel connections. Both pre- and
post-autostart data signals are available on the rear panel as are the inputs and outputs of two
separate high-level loop switches. The internal 175 Volt, 50 mA loop supply is also connected to
the rear panel. Thus, the demodulator output can be used to directly key the loop or be first
passed through additional signal processing (such as the popular UART and digital control devi-
ces), and then routed back through the ST-6000 keyer stages, with the option of using or not us-
ing the internal loop supply of the ST-6000. In addition, the ST-6000 has both output and input
signal connections that are compatible with both the EIA - RS-232C and MIL-STD-188C data signal
levels.
The ST-6000 also includes a Keyboard Operated Switch (KOS) circuit that can be used to auto-
matically switch the transmit receive control circuitry of the station. The KOS circuit senses tele-
printer keyboard and CW identification signal status. If either the keyboard or the CW-ID key is
used, the KOS switching transistor turns "ON" (low impedance to ground). The KOS circuit also
places the ST-6000 demodulator circuits in a "standby" status to prevent feedback from the receiv-
er while transmitting. The NPN KOS switching transistor can be used to control a DC relay that is
supplied from a positive voltage source or a push-to-talk (PTT) control line in a transmitter (provid-
ing the PTT line is derived from a positive DC source.) Since the KOS sensing line is connected to
the rear panel, it can also be triggered by external devices.
The audio input to the demodulator and the audio output from the tone keyer are both 500
Ohms balanced (or unbalanced if jumpered) with respect to ground and use audio transformers to
maintain DC isolation. The oscilloscope signals for a crossed-ellipse oscilloscope display are con-
nected to a rear panel connection. The ST-6000 is furnished with a front panel tuning oscilloscope.
Internal, electronically regulated ±12 Volt power supplies provide operating voltages for the de-
modulator, control and tone keyer sections of the ST-6000. A 175 Volt, 50 mA loop power supply is
also included as a part of that option. The main power transformer of the ST-6000 can be connect-
ed for operation with either 105 to 125 VAC or 210 to 250 VAC, 50 or 60 Hz power sources. Both
the power line and the loop power supply are fused with fuses accessible from the rear panel of
the unit. The ST-6000 requires approximately 20 watts of AC power and is housed in an attractive
brown and tan cabinet that matches the DS-3100 ASR and other HAL Communications Video Dis-
play Terminals. The cabinet can be supplied for either table or relay-rack mounting.
A complete set of cables and connectors are furnished with the ST-6000 to simplify the initial in-
stallation of the ST-6000. If you are anxious to try your ST-6000, it is suggested that you skip to
sections 3.1 and 3.2 of the installation chapter and then read sections 4.1 and 4.2 of the operation
chapter before turning the equipment on. The balance of this manual should then be studied be-
fore attempting any "custom" connections.

2-1
2. SPECIFICATIONS
Demodulator Section:
Input data: Serial Data
Data rate: Up to 110 baud
Input Impedance: 500 Ohms, balanced and isolated from ground
Input frequencies:
"Low-tone" set: Mark = 1275 Hz
Space = 1445 Hz (170 Hz shift)
1700 Hz (425 Hz shift)
2125 Hz (850 Hz shift)
"High-tone" set: Mark = 2125 Hz
2295 Hz (170 Hz shift)
2550 Hz (425 Hz shift)
2975 Hz (850 Hz shift)
"Special" tone sets Audio frequencies between 1200 and 3000 Hz; mark tone
must be common to all shifts; 850 Hz- maximum recommen-
ded shift.
Input signal amplitude: Full limiting (FM mode) for signal levels between –50 dBm and
+20 dBm (approximately 1 mV to 10 V rms). When "AM"
mode (non-limiting) is used, input signal should be in the
range –40 to +20 dBm (approximately 10 mV to 10 V).
lnput Filter -3 dB Bandwidth: 850 Hz shift - 1250 Hz
(all tone-sets) 425 Hz shift - 775 Hz
170 Hz shift - 275 Hz
Discriminator filters -3 dB
Bandwidth (all tone sets): 850 Hz shift - 180 Hz
425 Hz shift - 125 Hz
170 Hz shift - 70 Hz
Low-pass filter bandwidth: 82 Hz (minimum for 110 baud)
Tone Keyer Section:
Input data: Serial Data
Data rate: Up to 110 baud
Input signals: Can be externally connected for:
1. sensing of current loop
2. sensing of EIA-RS-232C signals
3. sensing of MIL-STD-188C signals
4. sensing of "dry" keyboard contacts
5. CW-ID key
6. CMOS-compatible signal
mark = 0 V
space = +12 V
Output tones: Standard - same tones as demodulator input
Special - any tones in the 1200 to 3000 Hz frequency range,
mark tone common to all shifts. In addition, a CW-ID tone is
generated 100 Hz below the mark tone; CW-ID = 1175 Hz for
"low-tones", 2025 Hz for "high-tones".
Output muting: Tone keyer output can be turned off and on via rear panel
connection (TONE ENABLE)
Tone accuracy: ±0.1 %

2-2
Tone amplitude: Adjustable from -40 dBm to 0 dBm (approximately 10 mV to
1.0 V)
Amplitude variation: Less than ±0.5 dB at 0 dBm output
Output impedance: 500 Ohms, balanced to ground
Distortion: All harmonics below the 9th are attenuated greater than
40 dB (Less than 1.0 % total harmonic distortion).
Control Section:
Autostart response time: Switch selectable: Slow = 3.5 sec.
Fast = 1.5 sec.
Motor control delay time: 20 seconds nominal
Antispace time: Space condition greater than 250 ms
KOS delay: Turn-on: Space condition longer than 5 ms or upon key
down of CW-ID key
Turn-off: Space condition longer than 500 ms or Mark
condition longer than 1 to 10 sec. (adjustable)
or 1 sec. after CW-ID key opening
KOS NPN switch transistor: Off: +25 VDC maximum
On: 500 mA maximum
Tuning Indicator: X - Y, 1" diameter oscilloscope display; rear panel connections
for additional oscilloscope.
Automatic Threshold Control: Performs DC level restoration to provide correction for bias
(ATC) distortion in received signals; can be disabled with front panel
switch.
Decision Threshold Hysteresis: Provides switching hysteresis to provide correction of distor-
tion caused by multipath propagation effects; can be disabled
with front panel switch.
Demodulator Outputs:
Current Loop: Two independent 250 Volt, 100 mA NPN switching transistors
that may be connected to the internal 175 Volt, 50 mA loop
power supply or to external supplies.
EIS - RS-232C compatible: Mark = –12 VDC
Space = +12 VDC
MIL-STD-188C Compatible: Mark = +6 VDC
Space = –6 VDC
CMOS compatible:
(4000 series, +12 supply): Pre-autostart data: Mark = 0 to +3.6 VDC
Space = +8.4 to +12.0 VDC
Post-autostart data: Mark = 0 to +3,6 VDC
Space = +8.4 to +12.0 VDC

2-3
Miscellaneous Data:
Fuse protection: Main AC Power - 0.5 A, slow-blow
Loop Power Supply - 0.1 A
Accessible from rear Panel
Power requirements: 105 to 125 or 210 to 250 VAC, 50 or 60 Hz, 20 Watts
(excluding printer motor)
Cabinet size: Width 17" (43.2 cm) - table | 19" (48.3) - rack
Height 3.5" (8.9 cm)
Depth 9" (22.8 cm)
Cabinet finish: Light tan front and rear panels
Textured brown top, bottom, and side panels
Baked vinyl paint to match HAL video terminals
Weight: 12.0 lbs (5.45 kg) net
15.0 lbs (6.82 kg) shipping
Front Panel Controls:
SHIFT (HZ) (3 switches): Select 170 Hz, 425 Hz or 850 Hz shift; controls both the de-
modulator and tone keyer sections.
LIMITER ON-OFF: Allows the demodulator section to be used in either limiting
(FM) or non-limiting (AM) modes.
SENSE NORM-REV: NORM = mark is lower tone
REV = mark is higher tone
Affects both the demodulator and tone keyer sections.
ATC ON-OFF: Turns Automatic Threshold Control on or off.
DTH ON-OFF: Turns Decision Threshold Hysteresis circuit on or off.
PRINT LINE-LOCAL: LOCAL = demodulator signals are inhibited to permit "local"
operation.
KOS ON-OFF: Turns the keyboard operated switch sensing circuit on or off.
AUTOSTART FAST-SLOW: FAST = 1.5 sec. response time.
SLOW = 3.5 sec. response time.
AUTOSTART ON-OFF: Turns the autostart circuit on or off.
POWER ON-OFF: Turns AC power to the demodulator on or off.
Oscilloscope:
INT: Controls intensity of oscilloscope trace
FOC: Controls focus of oscilloscope trace
VER: Vertical trace position control
HOR: Horizontal trace position control
Front Panel Indicators: Indicates correct tuning with the standard crossed ellipse pat-
Oscilloscope terns.
LOOP: LED lamp that is on when Loop 1 is in mark condition, regard-
less of autostart or LINE-LOCAL condition.
SPACE: LED lamp that is on whenever post-autostart data is in space
condition.
MARK: LED lamp that is on whenever pre-autostart data is in mark
condition.
KOS: LED lamp that is on whenever the KOS circuit is in transmit
condition.
AUTO: LED lamp that is on whenever the autostart circuit will pass
data.
POWER: AC power-on indicator.

2-4
Rear Panel Connections:
AC power input (unlabeled): Universal U.S./European standard connector for 120/240 VAC
non-captive AC power cords.
MOTOR: Three-prong AC socket to supply printer motor power con-
trolled by the autostart circuitry. The voltage available is the
same as the power line voltage to the ST-6000.
Ground (ground symbol) Cabinet ground connection for safety and RF ground connec-
tion.
AC POWER .5 A - SB: AC power fuse for ST-6000 only (not for the MOTOR socket).
LOOP .1 A: Loop power supply fuse.
LOOP 1 & 2: Main and auxiliary loop switch connections internal loop power
supply connection, CW-ID hand key connection.
LOOP 3: Additional series loop connection that can be used with loop 1
or loop 2.
KOS: KOS control line
Keyboard connection
RS-232 / MIL-188: Data input,/output connections for EIA-RS-232C and MIL-STD-
188C connections, CW-ID hand key connection.
SCOPE: Connection for external X-Y oscilloscope display.
AUXILIARY CONTROL: 15 pin connector to provide access to many control and signal
lines of the ST-6000. A circuit-board jumper plug is furnished
to make "normal" jumpers.
AUDIO OUTPUT: Balanced 500 ohm tone keyer output.
AUDIO INPUT: Balanced 500 ohm demodulator tone input.
NOTE: All of the above specifications are nominal, design-center values and may vary in produc-
tion units by as much as ±10 %. HAL Communications Corp. reserves the right to alter any
specifications without prior notification.

3-1
3. INSTALLATION
3.1 Initial Inspection
Upon receipt of the ST-6000, unpack and inspect it carefully for shipping damage. If evidence
of shipping damage is found, contact the carrier immediately. Before discarding the packing mate-
rial, check that all parts and accessories are accounted for. If any are missing, please notify the
factory or distributor in writing so that replacements can be supplied. The following parts and ac-
cessories are furnished with the ST-6000:
Accessory parts:
1 - Non-captive AC power cord
1 - 15 pin Auxiliary jumper plug (shipped in place on Auxiliary connector)
1 - 3 pin Loop 3 jumper plug (shipped in place on Loop 3 connector)
1 - Audio Input cable (phone to three pin male connector)
1 - Audio Output cable (phone to three pin female connector)
1 - Loop 1 cable (2-conductor cable to female 6 pin connector)
1 - KOS cable (2-conductor cable to male 3 pin connector)
1 - CW-ID and RS-232C Output cable (2, 2-conductor cables to 6 pin male connec-
tor, mates with RS-232 / MIL-188 connector)
12 ft - 2-conductor shielded cable
2 - 6 pin female connector shells (03-09-2061)
2 - 6 pin male connector shells (03-09-1061)
4 - 3 pin female connector shells (03-09-2031)
6 - 3 pin male connector shells (03-09-1031)
2 - 15 pin female connector shells (03-09-2152)
60 - male cable pins (02-09-2143)
24 - female cable pins (02-09-1143)
2 - 0.5 ampere, slow-blow fuses
2 - 0.1 ampere fuses
CAUTION: A SERIOUS SHOCK HAZARD MAY EXIST WHEN CONNECTING THE ST-6000 TO
OTHER EQUIPMENT. BEFORE MAKING ANY CONNECTIONS, BE SURE TO DISCON-
NECT THE ST-6000 AND OTHER EQUIPMENT FROM THE AC POWER LINE.
3.2 Use of Factory Supplied Cables
A total of five factory prepared cable-plug combinations and two jumper-plugs are supplied with
the ST-6000. These cables and plugs can be used to make most standard input and output con-
nections to the ST-6000, particularly those connections in which an ST-6 or similar demodulator is
being replaced by the ST-6000. The use of these standard cables and jumpers is discussed in the
following sections. Figure 3.1 shows in pictorial form some of the possible connections to these
standard cables.
3.2.1 Audio Input Connection
The audio input cable supplied mates with the rear panel audio input connector and has a pho-
no pin plug on the other end for connection to the station receiver. If the receiver output does not
have a phono connector, the plug may be cut off of the cable and replaced with the proper type,
or a new cable can be prepared using the procedures described in section 3.3.

3-2
3.2.2 Audio Output Connection
A factory-prepared cable is likewise provided for connection of the tone keyer output of the ST-
6000 to the station transmitter. This cable also has a phono plug connector which may be used or
removed as the particular connections dictate. The output level of the tone keyer is adjustable
with an internal control over the range of –40 dBm to 0 dBm. See section 4.13 of the operations
section for proper adjustment procedures. If a different audio output cable is required, see sect ion
3.3 for proper preparation procedures.
3.2.3 Loop 1 Cable Connection
There are three ways in which current-loop operated devices may be connected to the ST-6000;
"Loop 1", using the "Main" transistor keyer, "Loop 2", using the "Auxiliary" transistor keyer, and
"Loop 3", a jumper connection in series with the internal 60 mA loop power supply. The factory
supplied cables and jumper plugs are arranged so that the internal loop power supply, "Loop 3"
jumper, and "Loop 1" main keying transistor are series connected. "Loop 2" is not connected with
the standard cables and plugs. Alternate applications of the loop connections are discussed in sec-
tion 3.3.1. Current-loop sensing devices such as teleprinters and electronic displays and keyboards
can be connected to the nominal 60 mA loop circuit using the cable labeled "Loop I". If the device
is polarity sensitive (such as the DKB-2010 keyboard and the DS-3000 KSR Terminal), the white
wire is the "positive" connection and the black the "negative". The shield of the cable is NOT con-
nected in the loop circuit but is connected to the ST-6000 cabinet. The shield wire should therefore
be connected to the cabinet of the teleprinter or electronic device as a safety ground. A typical
connection to a 60 mA teleprinter is shown in Figure 3.1. Notice that the selector magnets and
keyboard contacts of the machine are series connected. Also, since the standard cables and jump-
ers connect the ST-6000 internal loop supply, an external loop power supply should NOT be includ-
ed in the loop circuit. Additional TTY equipment can be connected in the loop by breaking the
jumper on the LOOP 3 plug and series connecting the devices. On the LOOP 3 plug, pin 1 is posi-
tive, Pin 3 is negative, and pin 2 cabinet ground. Other loop connections possible with the stand-
ard cables are shown in Figure 3.2. Alternate loop connections are discussed in section 3.3.1.
3.2.4 Motor Power Connection
The power for the teleprinter motor can be supplied by the MOTOR connector of the ST-6000.
The power to this connector is controlled by the autostart relay of the ST-6000. The TOTAL current
supplied by this receptacle should not exceed 10.0 Amperes. The following precautions should be
observed when using the MOTOR receptacle:
1. The power to the MOTOR receptacle is NOT fused in the ST-6000. The user should be sure
that any device attached to this connector has its own fuse protection.
2. The AC voltage furnished on the MOTOR receptacle is the SAME as the AC power line volt-
age supplied to the ST-6000; if the ST-6000 is operated from a nominal 240 VAC power
line, the MOTOR receptacle also furnishes 240 VAC.

3-3

3-4

3-5
Note: The data connection between the DS-3100 and the ST-6000 is via a loop connection, not
an RS-232 connection. The "RS-232" connector on the ST-6000 is only used to connect the
CW-ID line to the demodulator.

3-6
Figure 3.? DS-2000 and ST-6000 System Connection Schematic

3-7
3.2.5 KOS Cable Connection
The wires from the KOS cable can be connected to the transmitter push-to-talk (PTT) control
line for automatic transmit-receive control of the station. The jumpers on the factory-supplied AUX-
ILIARY jumper plug allow operation of the KOS circuit when the keyboard and printer sections of
the teleprinter are series connected to LOOP 1 (or LOOP 3). A complete discussion of the operation
of the KOS-circuit is found in section 4.9. Alternate KOS circuit connections are also discussed in a
later section. The following precautions should be observed when using the KOS cable:
1. The KOS switching transistor in the ST-6000 is an NPN transistor. The transmitter push-to-
talk (PTT) line should have a positive voltage with respect to ground in receive condition.
2. Shunting the PTT line to ground should place the station in transmit mode.
3. The voltage of the PTT circuit should not exceed +25 Volts (receive).
4. The current drawn through the KOS transistor in transmit mode should not exceed 500 mA.
5. If negative or AC voltages are to be controlled by the KOS circuit, a DC relay should be
used to isolate the KOS and PTT circuits.
6. The KOS connection is to the white wire (+) and the shield wire (ground).
NOTES ON THE USE OF ST-6000 RS-232 I/O CONNECTIONS
1. Modify the standard Auxiliary Jumper Plug circuit board by adding a wire jumper between
Pin 13 (Transmit Loop Drive) and Pin 14 (Local Data Out).
2. Using the pins and connector shells provided, make a new jumper plug for the Loop 1 & 2
connector (J8). Connect a wire jumper between pin 1 (Loop High) and pin 4 (Loop Low);
connect a second wire jumper between pin 3 (Keyboard Data In) and pin 5 (Ground). Use a
six pin female shell and male pins.
3. Plug-in the standard Loop 3 jumper plug furnished.
4. Use the standard RS-232 I/O cable to connect to the terminal or machine.
The ST-6000 and terminal will now operate in the half-duplex mode using RS-232 I/O interface
connections. The RS-232 data from the terminal will both drive the ST-6000 Loop 1 circuit and op-
erate the KOS circuitry. A teleprinter connected into the Loop 1 circuit will print data generated on
the RS-232 terminal or data demodulated by the ST-6000. A keyboard can be connected in the
Loop 1 circuit, if desired.
RS-232 Full-duplex operation with the ST-6000:
The following steps should help clarify use of the RS-232 Input/Output connections for full-du-
plex operation with the ST-6000:
1. Refer to Figure 3.6 and modify the Auxiliary Jumper Plug circuit board as shown, removing
the circuit board jumpers between pins 1 and 5 and between pins 11 and 15; add a wire
jumper between pins 14 and 15.
2. Using the pins and connector shells provided, make a new jumper plug for the Loop 1 & 2
connector (J8). Connect a wire jumper between pins 1 and 4 and a second wire jumper be-
tween pins 3 and 5 of the plug. Use a six pin male shell and female pins.
3. Plug-in the standard Loop 3 jumper plug furnished.
4. Use the standard RS-232 I/O cable (as modified above) to connect to the terminal or ma-
chine.
5. Use the front panel switch to turn the KOS circuit OFF.
A printer may again be inserted in the Loop 1 circuit but will now print ONLY received data and not
data originating from the RS-232 terminal.

3-8
Figure 3.2 Loop Connections to the ST-6000

3-9
Figure 3.3 RS-232 I/O Connections to the ST-6000