Lectrosonics TH2 User manual

TH2
DIGITAL TELEPHONE HYBRID
LECTROSONICS, INC.
Rio Rancho, NM
OPERATING INSTRUCTIONS
and trouble-shooting guide

2
TABLE OF CONTENTS
INTRODUCTION ................................................................................................... 2
FCC PART 68 COMPLIANCE ............................................................................... 3
GENERAL TECHNICAL DESCRIPTION ............................................................. 4
INSTALLATION ...................................................................................................... 5
FRONT PANEL DESCRIPTION ............................................................................ 7
DIP SWITCH OPTIONS ........................................................................................ 7
REAR PANEL DESCRIPTION .............................................................................. 8
OPERATING INSTRUCTIONS ............................................................................. 9
TH2/AM8 SYSTEM SETUP PROCEDURE........................................................ 10
TROUBLESHOOTING ......................................................................................... 11
SERIAL CABLE WIRING DIAGRAM ................................................................. 12
AMX CABLE WIRING DIAGRAM ....................................................................... 12
AMX Programming Notes ............................................................................... 12
SERIAL PORT SOFTWARE COMMANDS ........................................................ 13
SPECIFICATIONS ............................................................................................... 16
ACCESSORIES ................................................................................................... 16
SERVICE AND REPAIR ...................................................................................... 17
RETURNING UNITS FOR REPAIR .................................................................... 17
WARRANTY ........................................................................................... Back cover
INTRODUCTION
The TH2 Digital Hybrid is part of the LecNetTM family of audio products. The TH2
works with any standard two wire telephone system, to provide a convenient and
inexpensive means of using any sound system for teleconferencing. This product is
microprocessor controlled, with a powerful Digital Signal Processor (DSP) actively
adjusting the line balance to achieve maximum transmit and receive signal separa-
tion. In addition, echo suppression based on Lectrosonics patented Adaptive Propor-
tional Gain algorithm (U. S. Patents No. 5402500 and 5414776) minimizes acoustic
echo while maintaining virtually full-duplex operation. The TH2 can be setup manu-
ally or with an IBM compatible PC in the PC Remote mode. Manual setup is accom-
plished by adjusting three trimmer potentiometers and a set of dip switches. Four
push-buttons and a wired remote control port provide a convenient way to control the
operation of the TH2 locally or remotely.

3
Digital Telephone Hybrid
Rio Rancho, NM – USA
FCC PART 68 COMPLIANCE
This equipment complies with Part 68 of the FCC rules. On the rear panel of this
equipment is a label that contains, among other information, the FCC registration
number and ringer equivalence number (REN) for this equipment. If requested, this
information must be provided to the telephone company.
This equipment uses the following USOC jacks: RJ11C
The REN is used to determine the quantity of devices which may be connected to the
telephone line. Excessive REN’s on the telephone line may result in the devices not
ringing in response to an incoming call. In most, but not all areas, the sum of the
REN’s should not exceed five (5.0). To be certain of the number of the devices that
may be connected to the line, as determined by the total REN’s, contact the tele-
phone company to determine the maximum REN for the calling area.
If this equipment causes harm to the telephone network, the telephone company will
notify you in advance that temporary discontinuance of service may be required. If
advance notice isn’t practical, the telephone company will notify the customer as
soon as possible. Also, you will be advised of your rights to file a complaint with the
FCC if you believe it is necessary.
The telephone company may make changes in its facilities, equipment, operations, or
procedures that could affect the operation of the equipment. If this happens, the
telephone company will provide advance notice in order for you to make the neces-
sary modifications in order to maintain uninterrupted service.
If trouble is experienced with this equipment, please contact Lectrosonics, Inc. at
[phone] for repair and/or warranty information. If the trouble is causing harm
to the telephone network, the telephone company may request you remove the
equipment from the network until the problem is resolved.
The following repairs can be done by the customer: No user serviceable parts
inside.
This equipment cannot be used on telephone company-provided coin service.
Connection to Party Line Service is subject to state tariffs.

4
GENERAL TECHNICAL DESCRIPTION
The TH2 is built around a powerful DSP which performs all internal calculations using 24 bits, providing an internal
dynamic range of 144dB. The DSP implements both the transmit/receive signal separation, as well as a sophisticated
echo suppression algorithm. The Lectrosonics Adaptive Proportional Gain algorithm (US patent #5,414,776 &
#5,402,500) used for echo suppression dynamically varies the transmit and receive path gain in response to the
signal level present in both paths. This helps prevent retransmission of a received signal caused by acoustic coupling
between near-end system loudspeakers and microphones. Because no abrupt gain changes are made, the per-
ceived effect is a full duplex conversation.
The TH2 is fully interfaced with the AM8 automatic mixer in that it participates in the auto mixing algorithm just like
another microphone. The transmit (or near-end) signal is typically received from the Lectrosonics AM8 Automatic
Mixer via the TH2 Expansion Out jack. When the near-end transmit signal is coming from any other line level source,
it is connected to the TH2 via the Local In/Out port (balanced or unbalanced). The Transmit Level control allows
adjustment of the transmit signal which is passed through a very fast attack limiter prior to being digitized by the 13 bit
A/D converter. The transmit output signal is converted back to an analog signal by the 13 bit D/A converter, buffered,
and output to the phone line coupling transformer.
The far-end signal is received from the phone line coupling transformer, buffered, digitized by the 13 bit A/D converter
and processed in the DSP chip. It is then converted back to an analog signal by the 13 bit D/A converter, and output
either to the Expansion or Local Out port (balanced or unbalanced). The Receive Level control allows adjustment of
the receive signal, while Volume Up/Dn pushbuttons regulate the received volume. LEDs indicate level changes and
show when limits are reached. Volume adjustment range is set with the combination of two dip switches from the front
panel. The Connect push-button connects the TH2 to the phone line, while the Privacy push-button mutes the transmit
path of the TH2, allowing private conversation to take place.
Because of impedance mismatches between the transmit output driver and the transformer and phone line, some of
the transmit signal recirculates through to the receive path. In a normal telephone handset, this recirculated transmit
signal is known as a “sidetone.” In teleconferencing applications, however, this sidetone signal can cause feedback
or loss of intelligibility. For this reason, the DSP is programmed to remove any artifacts of the transmit signal from the
receive signal. The Mix Out connector provides an unbalanced output signal for recording purposes (in the Expansion
or Local mode) consisting of a mix of the transmit and receive signals.
LIMITER A/D
D/A A/D
D/A
PHONE LINE
TELEPHONE
MIX OUT
LOCAL OUT +
LOCAL OUT –
VOLUME DN SW
CONNECT LED
CONNECT SW
PRIVACY SW
VOLUME UP SW
AUTO ANSWER
RX ATTEN
AUTO INITIALIZE
CONNECT LED
PRIVACY LED
PRIVACY LED
ECHO SUPPRESSION
2
ECHO SUPPRESSION 1
VOLUME LIMIT 1
VOLUME LIMIT 2
LOCAL IN +
LOCAL IN –
REMOTE CONTROL
INTERFACE
TRANSMIT
LEVEL
MIX OUT
LEVEL
RECEIVE
LEVEL
DIGITAL
SIGNAL
PROCESSOR
TX
SIG
TX
LIMIT
RX
SIG
RX
LIMIT
VOLUME UP
VOLUME DOWN
PRIVACY
CONNECT
OUT
IN
LECNET
(RS-232)
MAIN IN
MAIN OUT
EXPANSION
OUT
EXPANSION
IN
1
2
1
2
3
MIX MINUS OUT
MIX MINUS IN
AUTO MIX
LOG OUT
LOG
AMP
68HC705
uC
Figure 1 - TH2 Block Diagram

5
Digital Telephone Hybrid
Rio Rancho, NM – USA
INSTALLATION
PWR
IN
(CH40)
OUT IN
EXPANSION
20 VAC
LecNet
(RS232)
E
X
P
A
N
L
O
C
A
L
INPUT
Local Sound Reinforcement
TH2 Rear Panel
AM8 Rear Panel
Switch in "EXPAN" position
Switch in "MASTER" position
AM8 Rear Panel
Switch in "SLAVE" position
PWR
IN
(CH40)
OUT IN
MAIN OUT
+ –CH8 IN
EXPANSION REMOTE LEVEL
CONTROL
1 2 3 4
M
A
S
T
E
R
S
L
A
V
E
20 VAC
LECTROSONICS, INC.
LecNet
(RS232) DIR
OUT
+–
PWR
IN
(CH40)
OUT IN
MAIN OUT
+ –CH8 IN
EXPANSION REMOTE LEVEL
CONTROL
1 2 3 4
M
A
S
T
E
R
S
L
A
V
E
20 VAC
LECTROSONICS, INC.
LecNet
(RS232) DIR
OUT
+–
PWR
IN
(CH40)
OUT IN
EXPANSION
20 VAC
LecNet
(RS232)
E
X
P
A
N
L
O
C
A
L
LINE PHONE
MIX
LEVEL
+
IN OUT
+
LOCAL
MIN
OUT
OUTPUT
8-Channel Mixer
TH2 Rear Panel
Switch in "LOCAL" position
INPUT
Local Sound Reinforcement
IN 1 IN 2
OUT
2:1 Balanced
Mixer
Figure 2 - TH2 & AM8 Configuration
Figure 3 - TH2 & Single Bus mixer Configuration with
Balanced Outputs
WITH THE AM8 AUTOMATIC MIXER
(Figure 2)
Used with the Lectrosonics AM8 automatic mixer, the
interconnections to the TH2 are very simple. Set the
Local Expan switch on the TH2 to the Expan position. Set
the Master/Slave switch on the AM8 to the Master
position. Plug in the supplied 8-pin mini DIN cable as
shown in Figure 2. The TH2 will receive signals from the
AM8 and send signals to the AM8 via this single connect-
ing cable.
BALANCED INTERCONNECTION WITH NON-
LECTROSONICS MIXERS
(Figure 3)
For use with any non- Lectrosonics microphone mixer
and sound system, the Local/Expan switch on the TH2 is
set to the Local position. The cable connections are
made as shown in Figure 3 to maintain a balanced wiring
configuration. Note that the TH2 output signal at the Local
Out jack must be connected to the sound system outside
of the mixer that feeds the TH2. This typically requires the
use of a separate mixer ahead of the sound system
amplifier as illustrated in Figure 3.
An Unbalanced configuration is also possible using these
same jacks. For this configuration, leave the (-) uncon-
nected on the TH2 Local In/Out jack and use the (+)
terminal for signal hot.

6
PWR
IN
(CH40)
OUT IN
EXPANSION
20 VAC
LecNet
(RS232)
E
X
P
A
N
L
O
C
A
L
LINE PHONE
MIX
LEVEL
+
IN OUT
+
LOCAL
MIN
OUT
OUTPUT
8-Channel Mixer
TH2 Rear Panel
Switch in "LOCAL" position
INPUT
Local Sound Reinforcement
OPTIONAL UNBALANCED INTERCONNEC-
TION WITH NON-LECTROSONICS MIXERS
(Figure 4)
A simple method of mixing the incoming phone line signal
with the local microphone mixer output is illustrated in
Figure 4. This is an unbalanced configuration best suited
to short cable runs, such as with components rack
mounted next to each other. This configuration simplifies
the wiring connections and eliminates the need to install
an external mixer ahead of the sound reinforcement
system.
SIMULTANEOUS 2-WIRE/4-WIRE CONVER-
SION FOR 3-SITE CONFERENCING
BRIDGING
(Figure 5)
The TA1 Line Level Adapter is designed for connecting
an Audio/Video Teleconferencing Hybrid to the Lec-
trosonics AM8 automatic mixer.
With the AUTO MIX switch in the “ON”position, the video
codec (or other audio source) will participate in the
automatic mixing algorithm applied by the AM8 mixer. An
incoming signal from the far end of the telephone or
ISDN line will attenuate the gain on the local micro-
phones, reducing or eliminating acoustical coupling
between microphones and loudspeakers that could
cause a feedback loop.
Used with the AM8 mixer and TH2 telephone hybrid, 3-
site bridging is accomplished with the TA1 without the
need for any other mixing or routing devices.
PWR
IN
(CH40)
OUT IN
EXPANSION
20 VAC
LecNet
(RS232)
E
X
P
A
N
L
O
C
A
L
LINE PHONE
MIX
LEVEL
+
IN OUT
+
LOCAL
MIN
OUT
TH2 Rear Panel
Switch in "EXPAN"
position
AM8 Rear Panel
Switch in "MASTER"
p
osition
LECTROSONICS TA1
LINE LEVEL ADAPTER
EXP OUT EXP IN
AUTO MIX
OFF ON
PWR (CH40)
LEVEL
06
24
06
24
TA1 Front
Panel
TA1 Rear Panel
INPUT OUTPUT
Video
Codec
TA1 Rear
Panel
PWR
IN
(CH40)
OUT IN
MAIN OUT
+ –CH8 IN
EXPANSION REMOTE LEVEL
CONTROL
1 2 3 4
M
A
S
T
E
R
S
L
A
V
E
20 VAC
LECTROSONICS, INC.
LecNet
(RS232) DIR
OUT
+–
Figure 4 - TH2 & Single Bus Mixer Configuration with
Unbalanced Outputs
Figure 5 - 3-Site Conferencing Bridging

7
Digital Telephone Hybrid
Rio Rancho, NM –USA
FRONT PANEL DESCRIPTION
Figure 6 - TH2 Front Panel
POWER - Turns the TH2 On/Off. After the power is turned on, all LEDs, with the exception of the Privacy LED, will
turn ON momentarily.
RECEIVE LEVEL - Adjusts the receive volume level. The SIG LED next to this potentiometer indicates the presence
of receive signal, and the LIM LED indicates overload in the receive channel.
VOLUME UP/DOWN - Adjusts the receive audio level. Operates in parallel to the wired remote Volume Up/Down
buttons. The range of adjustment is set by the Volume Limit dipswitch settings. Note that the Connect LED will flash
each time a change in volume (up or down) is made. With the button held in, the flashing will stop when the volume
limits are reached.
Note: To reset the unit to factory defaults, hold in the Volume Up and Volume Down buttons while
turning on the Power until the LEDs flash. This will set the LecNet software mode to Local. Any saved Dipswitch
settings in the LecNet software control panel will be returned to the factory default settings of switch 3 and switch 5
ON.
TRANSMIT LEVEL - Adjusts the transmit volume level. The SIG LED indicates the presence of transmit signal, and
the LIM LED indicates overload in the transmit channel.
PRIVACY - Mutes the transmitted audio to allow private conversations to take place. The phone connection is main-
tained.
CONNECT - Connects or disconnects the TH2 from the phone line. The Connect button is used to pick up an incom-
ing call or to switch back and forth between the TH2 and a handset.
DIP SWITCH OPTIONS
Volume Limit - Selects the limitation placed on the volume adjustment
range. This limitation only affects the front panel Receive Level
pushbuttons, or the Receive Level pushbuttons of the wired remote
control (if used).
Auto Initialize - Selects whether the TH2 will re-initialize every time it
connects. If Auto Initialization is On, the far-end listener will hear a
short noise burst as the TH2 resets its adaptive filter coefficients. If
Auto Initialization is Off, the adaptive filter coefficients stored from the
system setup are used. The best performance will be obtained with
Auto Initialization turned On.
RX Atten - Selects the amount of input signal attenuation. It is usually
used in the 0dB position. If the Receive Lim LED is on with the Re-
ceive Level pot in the fully counterclockwise position, it is a good
indication that the incoming signal from the phone line is too “hot”and
that the dip switch should be set to the -10dB position. If the Receive
Lim LED does not turn off, please contact the factory for technical assistance.
Auto Answer - Selects whether the TH2 will automatically connect if it receives a phone call. Furthermore, it will
automatically disconnect the TH2 when the far-end party hangs up if the local PBX supports loop reversal on hangup.
When the TH2 automatically disconnects, a loop reversal impulse (approximately 10 seconds after the hangup) could
be heard from the local sound reinforcement system.
Echo Suppression - Selects the amount of echo suppression used. Auto is the normal setting. Auto uses the least
echo suppression possible to achieve acceptable performance. Use the other settings as necessary if too much of
the received signal is acoustically coupled back to the transmit signal.
LECTROSONICS, INC.
RIO RANCHO, NM U.S.A.
POWER
DIGITAL HYBRID
RX ATTEN
AUTO ANSWER
ECHO SUP 2
ECHO SUP 1
AUTO INIT
VOL LIMIT 1
VOL LIMIT 2
TRANSMIT
SIG LIMCONNECT PRIVACY
TRANSMIT
LEVEL
RECEIVE
SIG LIM
RECEIVE
LEVEL
UP DOWN
VOLUME
MIN MIN
7654321
21 212121
3 3
4 4
5 5
76 76
Echo
Suppression
Auto 12dB 18dB 24dB
76 76
Auto
Answer
Off On
Rx
Atten
Auto
Initialize
Volume
Limit
0dB –10dB
Off On
No Limit +3/-6dB+6/-6dB+6/-12dB
Figure 7 - TH2 Dip Switch Settings

8
REAR PANEL DESCRIPTION
Figure 8 - TH2 Rear Panel
PWR IN - connects to the CH40 power supply supplied with the unit.
LOCAL/EXPAN SWITCH - Sets the TH2 for use in conjunction with either the AM8 (expansion mode) or any other
line level Input/Output (local mode).
EXPANSION IN/OUT - Allows the TH2 to be connected to the Automatic Mixer AM8 and other LecNet devices. With
this connection the Receive signal is automatically mixed with other microphones using Lectrosonics’unique and very
effective Adaptive Level Proportional mixing algorithm* for local sound reinforcement purposes. Note: The TH2 must
be connected directly to the AM8. Other LecNet devices must be connected to the TH2 Expansion In connector.
LECNET (RS232) SERIAL PORT - Provides access to and remote control of some of the operational features of the
TH2. This port is compatible with the serial port of a PC, AMX touch screen, or any other controller with the standard
RS232 type serial port. Refer to Serial Port Software Commands
on page 13.
(WIRED) REMOTE CONTROL - Allows the Connect, Privacy and
Volume Up/Down momentary pushbuttons (and indicator LEDs) to
be operated from a remote location. Figure 9 shows the connec-
tion diagram to the 9 pin D-Sub Remote Control connector.
LOCAL IN(+), IN(-) - Accepts a line level balanced or unbalanced
transmit input signal. Typically this input is driven from the output of
a microphone mixer.
LOCAL OUT(+), OUT(-) - Outputs the received audio signal into a
sound reinforcement system.
MIX OUT - Provides an unbalanced signal consisting of a mix of
the transmit and receive signals. Generally used for recording both
sides of the conversation.
MIX OUT LEVEL - Controls the audio level of the Mix Output.
LINE - Accepts a standard two wire telephone line on an RJ-11
style connector.
PHONE - Accepts a standard RJ-11 style connector to enable a telephone to be used in conjunction with the TH2.
LINE PHONE
PWR
IN
(CH40)
OUT IN
EXPANSION
20 VAC
LECTROSONICS, INC.
LecNet
(RS232)
E
X
P
A
N
L
O
C
A
L
REMOTE CONTROL MIX
LEVEL
+
IN OUT
+
LOCAL
MIN
OUT
CONNECT
PRIVATE
VOL UP
VOL DOWN
PRIV LED
CONN LED
COMMON
1
2
3
4
6
7
8
COMPLIES WITH PART 68, FCC RULES
FCC REGISTRATION NUMBER:
RINGER EQUIVALENCE: 1.3B 4J3USA-23026-BR-N
VOLUME DOWN
VOLUME UP
PRIVACY
CONNECT
CONNECT LED
PRIVACY LED
54321
9876
RX SIG LED
TX SIG LED
Figure 9 - TH2 Remote Control Connector
U.S. PATENTS 5,414,776 and 5,402,500

9
Digital Telephone Hybrid
Rio Rancho, NM –USA
OPERATING INSTRUCTIONS
Setup of the TH2 consists of choosing the front panel dip switch options, setting transmit and receive levels located at
the front panel, and connecting the Input/Output in the proper configuration. Using the LecNetTM Control is covered
in the Serial Port Hardware and Software sections of this manual. When the power is turned on to the TH2 the LEDs,
with the exception of the Privacy LED, will momentarily turn On.
Note: To reset the unit to factory defaults, hold in the Volume Up and Volume Down buttons while turning on the Power
until the LEDs flash. This will set the LecNet software mode to Local. Any saved Dipswitch settings in the LecNet
Software control panel will be returned to the factory default settings of switch 3 and switch 5 ON.
1) Connect the CH40 power supply to the PWR IN jack of the TH2.
2) Connect the telephone line to the LINE input RJ-11 jack. If a local telephone is to be used in conjunction with the
TH2, connect it to the PHONE input RJ-11 jack. Note that to originate calls, a local phone must be connected to
the system.
3) Connect the audio Input/Output according to the desired configuration either through the Expansion or Local port
(refer to the Installation section of this manual paying particular attention to the LOCAL/EXP switch.)
4) Set the Transmit Level control and the Receive Level control to the mid position (12 o’clock). Set the Main Output
level control on the AM8 to the mid position.
5) Set the dipswitch options as desired. Factory settings are:
Echo Suppression: Auto Auto Answer: On
Rx Atten: 0dB Auto Init: On
Volume Limit: No Limit
6) If a local phone is connected, originate a call to a remote site. If no local phone is present, someone at a remote
site must call you. If you are the originating site, press the CONNECT button to connect the TH2 to the phone line
after the call has been established. If the remote site originates the call, and Auto Answer is On, the TH2 will
establish the connection automatically.
7) Adjust the receive volume level using the Receive Level control. Then adjust the transmit level using the Transmit
Level control, or Main Level on the AM8. If the Receive Lim LED is on with the Receive Level pot in the fully
counterclockwise position, it is a good indication that the incoming signal from the phone line is too “hot”and that
the Rx Atten dip switch should be set to the 10dB position. If the Receive Lim LED does not turn off, please
contact the factory for technical assistance.
8) When all volume levels are acceptable, disconnect the call by pressing the CONNECT button again.
9) If any limitation on the remote volume control range is desired, set the Volume Limit dip switches accordingly.
10) The TH2 revisions 1.1 and higher now include firmware support for the J7 DC Bypass jumper. This jumper can be
used to bypass the automatic disconnect circuitry on the TH2. This feature is intended to be used in installations
where the TH2 is connected to an outside
phone line through a PBX system which
does not supply DC battery. By changing the
position of the DC Bypass jumper, and by
selecting the dipswitch option AUTO AN-
SWER to OFF, the TH2 will be transfered to
fully manual operation. The factory default
position is Auto Disconnect.
J7
RUN
Auto
Disconnect
Manual
Disconnect
J7
RUN
F r o n t
R e a r
Figure 10 - Location of DC Bypass Jumper

10
TH2/AM8 SYSTEM SETUP PROCEDURE
When used in conjunction with one or more AM8’s, the following procedure will insure optimum operation. The
system architecture provides for algorithm-controlled gain paths that require the signal levels received by the TH2 and
the signal levels within the AM8 (microphone or other line level devices) be relatively equal. When this is achieved, a
very high quality teleconference results with seamless, near-duplex operation.
The following procedure will serve as a guide to balancing TRANSMIT (near end signal from the AM8) and RECEIVE
(far end signal received by the TH2) signal levels without the need for any external test equipment or computer:
1) Set the inputs of the AM8 for proper gain.
The first step is to select the appropriate mic preamp gain on the AM8. Most condenser and some wireless mics
would use +30dB gain setting, while most dynamic mics or if the mic to talker distance is great would use +50dB
gain setting; 0dB gain setting is used for devices capable of producing line level output signals (tape deck, CD
player, some wireless mics).
2) Adjust the individual CHANNEL LEVEL and MAIN LEVEL controls.
Start with the CHANNEL LEVEL and MAIN LEVEL controls on the AM8 at mid position and have someone talk
into one of the mics at a normal operating distance. Switch the COMP/LEVEL to the IN position and set the
THRESHOLD trim pot to “-10.”Now adjust the input channel level control so that only the right-most three LEDs
come on at the loudest peaks in the speakers voice, while during the normal speech no LEDs should be lit. The
proper adjustment of the COMP/LEVEL would cause compressor/leveler action only during the very loud speech
or if the participant leans very close to the mic.
If local sound reinforcement is not used in the room, turn the MAIN LEVEL to minimum since this pot will not
influence the TRANSMIT signal. If local sound reinforcement is incorporated in the room, adjust the MAIN LEVEL
pot and the volume on the power amplifier (PA) to the desired SPL in the room. Check each AM8 input’s contribu-
tion to the SPL in the room, and re-adjust the CHANNEL LEVEL such that all inputs are approximately at the
same SPL in the room. Note that the MAIN LEVEL and PA volume are essentially connected in series, so that if
you increase one and decrease the other, the SPL in the room should be about the same.
3) Establish an outside call.
The best results are achieved using a Plain Old Telephone System (POTS) line, or using a telephone line simula-
tor such as Teltone TLS-3, or TLS-4. When setting up the TH2, establish a call “off-site”and adjust for the average
of several calls since there might be some difference in received levels from one call to another. It is best to avoid
calling from an “in-house”extension within the same PBX or KSU, since such a call would typically be 6-10dB
louder than an outside call. Furthermore, initially avoid test calls from the bridging service since they are typically
6-10dB quieter than an outside call.
4) Adjust the RECEIVE LEVEL trim pot.
Starting from the mid position on the RECEIVE LEVEL trim pot on the TH2, adjust the level so that the incoming
call is heard through the local PA system at about the same SPL as the AM8 inputs (mics and line level devices).
If local sound reinforcement is not used, adjust the RECEIVE LEVEL to the desired SPL in the room. In both
cases, the RECEIVE SIG LED will be lit when far-end signal is received through the TH2.
If the RECEIVE LIM LED is lit, you are clipping the signal either at the output, or internally in the Digital Signal
Processor (DSP). Back off on the RECEIVE LEVEL all the way to the minimum - if the LIM LED is not lit, your
RECEIVE LEVEL was too high. If the LIM LED is still lit, your phone line signal is “too hot”, and you need to
switch the RX ATTENUATE dipswitch to -10dB position to prevent DSP internal clipping. After the dipswitch
positioning, adjust the RECEIVE LEVEL to the desired SPL in the room.

11
Digital Telephone Hybrid
Rio Rancho, NM –USA
5) Adjust the TRANSMIT LEVEL trim pot.
Starting from the mid position on the TRANSMIT LEVEL trim pot, adjust for the proper TRANSMIT level. The
TRANSMIT SIG and LIM LEDs are useful tools to determine the appropriate TRANSMIT LEVEL. Make sure that
TRANSMIT SIG is lit when someone speaks into the microphone, but back-off the TRANSMIT LEVEL if TRANS-
MIT LIM LED lights.
6) Fine tune the Lectrosonics system to the room acoustic response.
Sometimes, customer expectations are higher than what the audio teleconferencing system can provide. Every
conference room will have a different audio response, and each system can be readjusted to its limits - but you
can not achieve better response than that allowed by the positioning of microphones, speakers, and overall
acoustic signature of the room. Here, we will attempt to describe some common problems when setting up a
teleconferencing system.
a) If customer expectation is to have a loud receive signal, some of the sound will eventually be recirculated.
You can see this behavior on the front panel of the TH2 when RECEIVE LED and TRANSMIT LED are lit at
the same time. To correct this problem, either you have to reduce the microphone CHANNEL LEVEL, reposi-
tion the microphones/speakers for different acoustic response of the room, or simply reduce the RECEIVE
LEVEL.
b) If customer expectation is to have a loud transmit signal, by increasing the TRANSMIT LEVEL, the signal
level balance between the transmit and receive inside the DSP is disturbed, potentially causing the TH2 to
diverge. You should try to reconverge the DSP filter by 1) lifting up the local phone set, disconnecting the
TH2, waiting 2-3 seconds, and than re-connecting the TH2, or 2) re-initializing the digital filter through the
software control panel.
TROUBLESHOOTING
SYMPTOM POSSIBLE CAUSE
No receive sound from TH2 1) Receive Level control not turned up
2) Connect LED not lit (push connect switch)
3) Phone line from wall jack to TH2 not connected
No transmit sound from TH2 1) Transmit Level control not turned up to remote site
2) The Privacy LED is lit (push privacy switch)
3)The Local/Expan switch is not in the correct position
Feedback or hollow sound 1) RECEIVE LEVEL control turned up too high.
2) Not enough Echo Suppression (increase Echo Suppression)
3) Large variations in phone line impedance (set Auto Initialize On),
or re-initialize the digital filter.
Signal degredation when used in conjuction 1) Re-initialize the digital filter “on the fly”through the software
with the bridging service or DTMF cards control panel without breaking the telephone connection.

12
SERIAL CABLE WIRING DIAGRAM
Wiring Diagram, 9 Pin D-Sub
LecNet Device to PC
3.5MM
Stereo Plug
9 or 25 Pin Female
D-Subminiature
S
R
T
1
2
3
4
5
6
7
8
9
LecNet Port
LecNet Device Transmit
LecNet Device Receive
Gnd
Tip
Ring
Sleeve
Host
Serial
Port
(PC)
N/C
N/C
Wiring Diagram, 25 Pin D-Sub
LecNet Port
LecNet Device Transmit
LecNet Device Receive
Gnd
Tip
Ring
Sleeve
3
2
7
1
4
5
6
20
CD
RX
TX
Gnd
RTS
CTS
RI
RX
TX
Sig Gnd
Chassis Gnd
RTS
CTS
Host
Serial
Port
(PC)
DTR
DSR
DSR
DTR
LecNet Device to AMX or Crestron
LecNet Port
AMX
or
Crestron
Port
1
2
3
4
5
6
7
8
9
LecNet Device Transmit
LecNet Device Receive
Gnd
RXD
TXD
Gnd
Tip
Ring
Sleeve
3.5MM
Stereo Plug
9 Pin Female
D-Subminiature
S
R
T
N/C
N/C
N/C
N/C
N/C
N/C
The serial port on the LecNet device is a minimal RS-232 implementation. The figure shows the wiring diagram to
accommodate interconnection with either a 9 or a 25 pin serial port on a PC or other serial device.
AMX Programming Notes
If you are using an AMX system to control your LecNet
equipment, you’ll want to purchase the Lectrosonics
PT3 Protocol Translator. The PT3 connects between
the AMX bus and any LecNet equipment. With the
PT3, the LecNet equipment looks just like native AMX
equipment. The PT3 is the fastest and most productive
way to control LecNet devices with an AMX system.

13
Digital Telephone Hybrid
Rio Rancho, NM –USA
SERIAL PORT SOFTWARE COMMANDS
All LecNet devices use a modification of the typical one-to-one connection between two RS-232 compatible devices.
LecNet devices have both an RS-232 transmitter and receiver section. The transmitter section is “tri-stated”, or placed
in a high impedance mode, until the particular device is addressed. To facilitate the simple parallel connection of
multiple devices on a single RS-232 port, an addressing scheme is employed to route commands from the host to the
proper LecNet device. When a device receives its address from the host computer, it temporarily turns on its RS-232
transmitter long enough to send whatever data is requested by the host. In this way, multiple devices may drive a
single transmit signal back to the host, because only the addressed device will turn on its transmitter.
Valid address values are 128-254 (80 hex-FE hex). 255 (FF hex) is an invalid address and must not be used. Because
a LecNet device will interpret any single data byte whose value is greater than 127 as an address, single byte data (as
opposed to addresses) sent from the host must be in the range of 0-127. If a data value needs to be sent from the
host that exceeds 127, the host must format two bytes of output such that the first byte is the lower 7 bits of the 8 bit
value, and the second byte is 1 if the MSB of the data byte is 1, or 0 if the MSB of the data byte is 0.
All interchange of commands and data with any LecNet device should be done in hex rather than ASCII. The only
exception to this is the return data on the Get Device Name command (see command description below).
Each LecNet command must be preceded by the address of the device to be controlled. If a device with the requested
address exists on the system, it will respond by sending a 0 (0 hex, not ASCII) back to the host. Thus, each inter-
change with a LecNet device follows this pattern:
1) Host sends device address (133) in hex (1 byte);
2) Host receives byte of 0 hex from the LecNet device as acknowledgment;
3) Host sends command (1 byte, hex) to the LecNet device;
4) Host and LecNet device exchange data based on particular command sent.
Note that some LecNet commands cause LecNet devices to return an additional acknowledgment byte of data to
confirm the end of a transaction. This is most typical of commands that cause the LecNet device to be busy for more
than a few milliseconds processing the command. The additional acknowledgment byte lets the host know that the
LecNet device is no longer busy and can receive more commands. If a command does return an additional acknowl-
edgment byte, this will be explicitly stated in the command description.
As an example of a specific interchange between a host and an TH2 the following general procedure would be used
to get a name string back from an TH2:
Set up the communications parameters of the device which will be the host. The correct parameters for all LecNet
devices are 9600 baud, no parity, 8 data bits, 1 stopt bit. This must only be done once when the host is initialized.
1) Host sends device address. For a factory default TH2, this would be 133, or 85 hex (1 byte);
2) Host receives byte of 0 hex from the TH2 as acknowledgment;
3) Host sends command 1 hex (1 byte) to the TH2 to get the name data;
4) The LecNet device sends to the host 4 bytes. The first byte is 3 hex, which is the number of bytes in the
TH2’s name string. The TH2 will then send the ASCII characters “T”, “H”, and “2”to the host.
The following section is a listing of available commands grouped based on the TH2 function to which the commands
are related. The word “Host”in the command descriptions means the IBM PC or compatible, AMX controller, or
Crestron controller to which the TH2 is connected. Note that Lectrosonics supplies AMX include files for controlling all
LecNet devices. These files are included on the LecNet Master Pro setup disks which ship with each LecNet device.
The files are automatically installed on your system during the LecNet installation. If you use the default setup
subdirectory of “c:\lecnet”, the AMX include files will be found in “c:\lecnet\amx”.
There are several “status”flags that may be set by the host computer. Those flag commands that store the new value
in EEPROM will continue to have the new value even if the power to the TH2 is turned off.
The following commands are described from the perspective of the host. A “Get”command allows the host to receive
information from the TH2. A “Set”command allows the host to send information to set some parameter in the TH2.

14
General Device Commands
Get Device Name - Causes the TH2 to send its “name”string back
Host sends command - dec 1 or hex 01
Host receives data bytes: byte 1 is the length of the name string (3 for TH2), bytes 2, 3, and 4 are the ASCII repre-
sentation for the device name “TH2”, i.e. dec (84, 74, 50). or hex (54, 4A, 32)
Set Device Address - Changes the TH2 device address and stores the new address in EEPROM.
Host sends command - dec 2 or hex 02
Host sends 1 byte representing device address of valid range 128 to 254.
Get Firmware Version
Host sends command - dec 25 or hex 19
Host receives 1 byte representing firmware version stored in MCU. For example, version 1.1 would be received as dec
11 or hex 0B.
PC Local/Remote Mode Commands
Set PC Local/Remote Mode - forces change of mode by storing new mode in EEPROM
Host sends command - dec 11 or hex 0B
Host sends 1 byte which gets stored in EEPROM; 0 represents PC local mode, while 1 represents PC remote mode.
Host receives 1 byte representing the acknowledge byte.
Get PC Local/Remote Mode
Host sends command - dec 12 or hex 0C
Host receives 1 byte corresponding to the current TH2 mode; 0 represents PC local mode, while 1 represents PC
remote mode.
Get DSP Version
Host sends command - dec 127 or hex 7F
Host receives one byte representing DSP version
Re-initialize Digital Filter
Host sends command - dec 126 or hex 7E
This will reconverge the digital filter coefficients without loosing the telephone connection. This is very useful when a
bridging service or DTMF cards change the impedance of the line.
Dip Switch Commands
Set Dip Switch Positions
Host sends command - dec 13 or hex 0D
Host sends 1 byte which gets stored in EEPROM; byte representation is as follows:
BIT# FUNCTION
0 Echo Suppression 1
1 Echo Suppression 2
2 Auto Answer
3 Auto Attenuation
4 Auto Initialize
5 Volume Limit 1
6 Volume Limit 2
7 Not Used
Host receives 1 byte representing the acknowledge byte.
Get Dip Switch Positions
Host sends command - dec 14 or hex 0E
Host receives 1 byte, whose representation is the same as in “Download Dipswitch Positions”above

15
Digital Telephone Hybrid
Rio Rancho, NM –USA
PC Remote Control Commands
Set PC Remote Volume Up Flag
Host sends command - dec 15 or hex 0F
Host sends 1 byte representing the PC remote volume up status. This byte has a value of “1”when the Volume Up
button is pressed.
Set PC Remote Volume Down Flag
Host sends command - dec 16 or hex 10
Host sends 1 byte representing the PC remote volume down status. This byte has a value of “1”when the Volume
Down button is pressed.
Set PC Remote Privacy Flag
Host sends command - dec 17 or hex 11
Host sends 1 byte representing the privacy status. This byte has a value of “1”when the Privacy button is pressed.
Set PC Remote Connect Flag
Host sends command - dec 20 or hex 14
Host sends 1 byte representing the connect status. This byte has a value of “1”when the Connect button is pressed.
Get Connect Status
Host sends command - dec 22 or hex 16
Host reads 1 byte representing the connect status. This byte has a value of “1”when the TH2 is connected, and has a
value of “0”when the TH2 is disconnected.
Get Privacy Status
Host sends command - dec 23 or hex 17
Host receives 1 byte representing the privacy status. This byte has a value of “1”when Privacy is ON, and has a value
of “0”when Privacy is OFF.
Get Receive Gain Status
Host sends command - dec 21 or hex 15
Host receives 1 byte representing the current receive gain level (refer to the table below.)
Decimal Hex Decimal Hex Decimal Hex
Data Data Gain Data Data Gain Data Data Gain
0 00 [phone]D -7
1 01 [phone]E -8
2 02 [phone]F -9
3 03 +3 10 0A -4 16 10 -10
4 04 +2 11 0B -5 17 11 -11
5 05 +1 12 0C -6 18 12 -12
6 06 0 19 13 Off

16
SPECIFICATIONS
Connectors:
Audio: 8-pin mini DIN and depluggable terminal blocks
Telephone/Line: RJ-11 Modular
Wired Remote Control: DB-9
Output Audio: Actively balanced
Output Impedance: 200 Ohms, balanced; 100 Ohms unbalanced
Input Audio: Actively balanced, RF filtered
Input Impedance: 20k Ohms, balanced; 20k Ohms, unbalanced
Telephone Hybrid: Standard hybrid transformer with DSP line return cancellation
Auto Answer/Disconnect: Selectable - answers after first complete ring;
Hangs up after loop reversal
Volume Control: Local and Remote
Range: +6dB to 12dB and Off in 1dB steps.
Range Limit: Selectable - No limit; +6dB/-12dB; +6dB/-6dB;+3dB/-6dB
Echo Suppression: Selectable: Auto, 12dB, 18dB, 24dB
Call Frequency Response: ±3dB 300Hz to 3.5kHz
Caller THD (250Hz to 3.3kHz): Less than 0.2% (Receive Limit LED On)
Send THD (250Hz to 3.3kHz): Less than 0.2% (Transmit Limit LED On)
Maximum Output Level: +18dBu
Serial Communication (RS-232): 9600 baud, 8 data bits, no parity, 1 stop bit
Power Requirements: 280mA at 20VAC
Power Consumption: 10 Watts max at 20VAC
Weight: 3 lbs.
Dimensions: 19" wide, 1.75" high, 4.75" deep
Specifications subject to change without notice.
ACCESSORIES
Part Number Description
Standard
21552 15 ft. Telephone cable with RJ-11 connectors
21553 9-pin male D-sub connector
21554 Shell for 9-pin D-sub connector
21551 12" mini DIN expansion cable
21529 9-pin D-sub to stereo mini plug serial cable
CH40 110V AC power supply
LNETWIN 3.5" floppy disk with LecNet software
M-TH2 TH2 instruction manual
35679 mini straight slot screwdriver
Optional
RCW-TEL Wall plate remote control unit.
RCW-DESK Table top remote control unit

17
Digital Telephone Hybrid
Rio Rancho, NM –USA
SERVICE AND REPAIR
If your system malfunctions, you should attempt to correct or isolate the trouble before concluding that the equipment
needs repair. Make sure you have followed the setup procedure and operating instructions. Check out the intercon-
necting cords and then go through the TROUBLE SHOOTING section in the manual
We strongly recommend that you do not try to repair the equipment yourself and do not have the local repair shop
attempt anything other than the simplest repair. If the repair is more complicated than a broken wire or loose connec-
tion, send the unit to the factory for repair and service. Don’t attempt to adjust any controls inside the units. Once set
at the factory, the various controls and trimmers do not drift with age or vibration and never require readjustment.
There are no adjustments inside that will make a malfunctioning unit start working.
LECTROSONICS service department is equipped and staffed to quickly repair your equipment. In-warranty repairs are
made at no charge in accordance with the terms of the warranty. Out of warranty repairs are charged at a modest flat
rate plus parts and shipping. Since it takes almost as much time and effort to determine what is wrong as it does to
make the repair, there is a charge for an exact quotation. We will be happy to quote approximate charges by phone for
out of warranty repairs.
RETURNING UNITS FOR REPAIR
You will save yourself time and trouble if you will follow the steps below:
A. DO NOT return equipment to the factory for repair without first contacting us by letter or by phone. We need to know
the nature of the problem, the model number and the serial number of the equipment. We also need a phone number
where you can be reached 8 am to 4 pm (Mountain Standard Time).
B. After receiving your request, we will issue you a return authorization number (R.A.). This number will help speed
your repair through our receiving and repair departments. The return authorization number must be clearly shown on
the outside of the shipping container.
C. Pack the equipment carefully and ship to us, shipping costs prepaid. If necessary, we can provide you with the
proper packing materials. UPS is usually the best way to ship the units. Heavy units should be “double-boxed”for safe
transport.
D. We also strongly recommend that you insure the equipment, since we cannot be responsible for loss of or damage
to equipment that you ship. Of course, we insure the equipment when we ship it back to you.
Mailing address: Shipping address: Telephones:
Lectrosonics, Inc. Lectrosonics, Inc. Regular: [phone]
PO Box 15900 581 Laser Rd. Toll Free [phone]
Rio Rancho, NM 87174 Rio Rancho, NM 87124 FAX: [phone]
USA USA
World Wide Web: http://www.lectrosonics.com Email: [e-mail]

LIMITED ONE YEAR WARRANTY
The equipment is warranted for one year from date of purchase against defects in
materials or workmanship provided it was purchased from an authorized dealer. This
warranty does not cover equipment which has been abused or damaged by careless
handling or shipping. This warranty does not apply to used or demonstrator equip-
ment.
Should any defect develop, we will, at our option, repair or replace any defective
parts without charge for either parts or labor. If we cannot correct the defect in your
equipment, we will replace it at no charge with a similar new item. We will pay for the
cost of returning your merchandise to you.
This warranty applies only to items returned to us, shipping costs prepaid, within one
year from the date of purchase.
This warranty gives you specific legal rights. You may have additional legal rights
which vary from state to state.
LECTROSONICS, INC.
581 LASER ROAD
RIO RANCHO, NM 87124 USA
May 10, 2000