Lectrosonics M175 User manual

M175
Belt Pack Transmitter
LECTROSONICS, INC.
Rio Rancho, NM
OPERATING INSTRUCTIONS
and trouble-shooting guide

2
TABLE OF CONTENTS
INTRODUCTION .................................................................................................. 2
GENERAL DESCRIPTION .................................................................................. 3
CONTROLS AND FUNCTIONS .......................................................................... 4
BATTERY INSTRUCTIONS ................................................................................. 5
OPERATING INSTRUCTIONS ............................................................................ 6
TROUBLESHOOTING ......................................................................................... 7
SPECIFICATIONS AND FEATURES................................................................... 8
SERVICE AND REPAIR ....................................................................................... 9
RETURNING UNITS FOR REPAIR ..................................................................... 9
WARRANTY ......................................................................................... Back cover
INTRODUCTION
Thank you for selecting the M175 Wireless Microphone Transmitter. The M175
Series transmitters operate on high band frequencies from 150 MHz to 216 MHz. It
is offered in three different versions to meet your specific needs. This manual
covers all versions.
Only the M175 series transmitters are covered in this manual. Receivers are
covered in separate manuals. All versions of the M175 Series transmitters will
operate with any Lectrosonics high band VHF receiver. A frequency matched
transmitter/receiver combination makes up a “wireless system”.
If you are new to wireless microphones, you will discover a new freedom of move-
ment and level of convenience. If you are an experienced wireless user, you will be
pleased with the versatility and superior performance of the M175 design.
M175 Series transmitters are FCC type accepted under the following Parts:
Part 90 (150-172 MHz), Part 74 (174-216 MHz)

3
Belt Pack Transmitter
Rio Rancho, NM – USA
GENERAL DESCRIPTION
The M175 Series transmitter is offered in three versions. The standard model is the M175. The
M175-LS has an additional audio mute switch on the front panel, and the M175DC has a proprietary
Digital Code Squelch* circuit to eliminate squelching problems caused by interference.
The digital code system provides much more reliable control over the receiver audio output than a
conventional squelch can provide. The transmitter generates an 8-bit code at turn on, and another
code at turn off, to open and close the audio output on the receiver. The squelch on the receiver
cannot be opened by anything other than the specific code it is programmed to receive. This type of
squelch system is even more important when the receiver is connected into an automatic mixing
system.
The M175 transmitter uses the microphone cord for the antenna. This feature eliminates the need
for the “dangling wire” antenna found on many transmitters.
The M175 Series transmitters use a crystal controlled oscillator and temperature compensation
circuitry to ensure that the transmitter does not drift over time or with age.
To suppress audible noise, a “compandor” noise reduction circuit is used which is compatible with all
Lectrosonics 170 series, 175 series, and 185 series receivers. In addition, the input limiting circuit
will absorb 12 dB of overload without distortion. The audio circuitry is extremely quiet, with low
distortion for natural reproduction of either voice or music. The wide input adjustment range of M175
Series transmitters allows the use of virtually any microphone. The M175 can even be used with line
level inputs such as tape recorders or musical instruments.
The M175 Series transmitters operate from a replaceable standard 9 Volt alkaline battery. A preci-
sion battery test circuit continuously monitors the battery voltage. A highly visible LED glows as long
as the battery voltage is high enough to operate the transmitter. A 9 Volt alkaline battery will provide
up to 15 hours of operation.
The electret microphone input jack provides 5 Volts DC positive bias for all Lectrosonics’ electret
microphones. Many other electret microphones may be adapted to the M175 Series by making
simple wiring changes in the microphone connector.

4
CONTROLS AND FUNCTIONS
The MIC JACK is a locking micro jack that supplies “phantom power” for electret microphones such as the
Lectrosonics M130, M140 and the HM142V and HM152V headset models. Insert the microphone cord plug into the
jack and
rotate it clockwise to lock it . It is important that the plug be securely locked, since the microphone cord
serves as the antenna for the transmitter.
The POWER ON/OFF switch turns the power on and off. The switch should be left in the off position when the
transmitter is not in use. When the switch is in the on position, the battery will be drained even though the transmitter
is not being used.
The BATTERY INDICATOR LAMP will light when the transmitter is turned on and will stay lit as long as the battery is
good. As the battery voltage drops, the lamp will grow dim and finally go out.
The GAIN ADJUST is a recessed screwdriver adjustment used to match the gain of the transmitter to different
microphones, individual voices or other audio inputs such as tape deck outputs.
The AUDIO MUTE SWITCH (M175-LS only) is a toggle type on-off switch used to shut off the audio signal without
shutting off the RF carrier of the transmitter.
(Note: The M175DC, Digital Code Squelch version is operationally identical to the standard M175.)
LECTROSONICS
OFF
ON
–
+
M175
PWR
MIC
LEVEL
MIC
LECTROSONICS
OFF
ON
–
+
M175-LS
AUDIO
OFF
PWR
MIC
LEVEL
MIC
OFF
ON
M175-DC
PWR
MIC
LEVEL
MIC
LECTROSONICS
DIGITAL
CODE
Audio Switch
Battery Indicator Lamp
Power ON/OFF Switch
Mic Level Adjust
Microphone Jack
Belt Clip

5
Belt Pack Transmitter
Rio Rancho, NM – USA
BATTERY INSTRUCTIONS
The battery you use in the M175 Series transmitter should be a 9 Volt alkaline, available almost everywhere. An
alkaline battery will provide up to 15 hours of operation. Carbon zinc batteries, even if marked “heavy duty”will only
provide about 4 hours of operation. Rechargeable batteries made to look like 9 Volt batteries typically only produce
7.2 Volts at full charge, which will only operate the transmitter for an hour or less. Make sure your batteries are
marked “alkaline.”Short battery life is almost always caused by weak batteries or batteries of the wrong type.
The BATTERY LAMP will light when the transmitter is turned on and will stay lit as long as the battery is good. As
the battery voltage drops, the lamp will grow dim and finally go out. Even after the lamp goes out, there may still be
up to an hour or more of operating time remaining. When the battery voltage is too low for proper transmitter opera-
tion, the sound from the wireless system may be distorted, intermittent or totally absent. When the transmitter is first
turned on, the lamp may light for a short while even with a bad battery. It is good practice to check the brightness of
the lamp after the transmitter has been on for several minutes and to note the brightness occasionally during use.
To replace the battery, open the bottom battery door cover with your thumb, rotate the door until it is perpendicular
with the case and allow the battery to fall out of the compartment into your hand. It is difficult to install the battery
backwards. Observe the large and small holes in the battery contact pad before inserting a new battery. Insert the
contact end of the battery first, making sure the contacts are aligned with the holes in the contact pad, and then
swing the door closed. You will feel it snap into place when it is fully closed.
To open the battery
compartment door, push the
door up and away from the case
with your thumb, then swing
open.
1
2

6
OPERATING INSTRUCTIONS
This section covers adjustments to the transmitter that must be made before the wireless microphone system is
placed into operation. The step-by-step procedures are listed in the order in which they should be performed:
1) Turn the wireless receiver power on and make any required preliminary adjustments in accordance with instruc-
tions in the receiver operating instructions.
2) Plug the microphone into the transmitter. If you are using a lavalier or headset microphone, rotate the plug
clockwise to make sure the connection is locked.
3) Turn the transmitter power on and verify that the red lamp on it lights. If the lamp is very dim or does not light,
replace the battery.
4) Observe that the RF lamp on the receiver control panel is lit. This verifies that the receiver is receiving a useable
radio signal from the transmitter.
5) Position the microphone on your person in the location it will be used during actual operation. If a headset micro-
phone is being used, adjust the headband for a comfortable fit with the “gooseneck”to the left side of your head.
Position the microphone element at the corner of the mouth and rotate the white volume control fully clockwise.
The headset is designed to be worn over the head, but can also be worn around the neck. Do not position the
microphone pickup directly in front of your mouth as this may cause unwanted noise from breath pops as you
speak.
6) A small screwdriver is supplied with the transmitter. The screwdriver is used to adjust the audio gain of the
transmitter to match your microphone and your voice. The GAIN ADJUST is located on the control panel of the
transmitter as shown below. The adjustment is made while observing the modulation level lamps on the receiver
control panel:
a) Speak at the voice level you will be using during actual operation.
b) While speaking, adjust the transmitter gain until the green modulation lamp on the receiver (may be marked “-
20”) is lit or flickers and the red modulation lamp blinks only on the loudest words. Raise and lower your voice
while observing the lamps. The red lamp should blink only occasionally.
NOTE: The modulation lamps on some receivers are marked or colored differently than just
described. Consult the operating manual for the receiver in use.
7) You may now adjust the receiver output level (wireless microphone or mic volume, level, or volume attenuator) to
the desired audio output level. Consult your receiver manual if you are not sure of the location of these controls.
The GAIN ADJUST is used only to adjust for proper modulation level lamp indications. DO NOT use it to adjust
the audio output level of the receiver. Different voices and different microphones will usually require readjustment
of the transmitter gain control, so check the adjustment frequently. If several different people will be using the
transmitter, and there is not time to make the adjustment for each individual, adjust it for the loudest voice.
0dB
-20
MODULATION
GREEN RED
WHILE SPEAKING
ADJUST THE TRANSMITTER
AS YOU OBSERVE THE LEDs
ON THE RECEIVER
MOD LEVEL LEDs
(FULL SIZE RECEIVERS)
MODULATION LEDs
(MINIATURE RECEIVERS
)
(BOTH LEDs ARE RED)
TRANS
MITTER
MOD
LEVEL

7
Belt Pack Transmitter
Rio Rancho, NM – USA
TROUBLESHOOTING
Before going through the following chart, be sure that you have a good battery in the transmitter. It is important that
you follow these steps in the sequence listed.
SYMPTOM POSSIBLE CAUSE
TRANSMITTER BATTERY LED OFF 1) Unit turned off. Check front panel on/off slide switch.
2) Battery is inserted backwards.
3) Battery is dead.
RECEIVER RF LAMP OFF 1) Transmitter not turned on.
2) Transmitter battery is dead.
3) Receiver antenna missing or improperly positioned.
4) Transmitter and receiver not on same frequency. Check
labels on transmitter and receiver.
5) Operating range is too great.
NO SOUND AND RECEIVER MOD LEVEL LEDs ARE OFF
1) Transmitter audio muted (M175-LS only)
NO SOUND BUT RECEIVER MOD LEVEL LEDs ARE ON
1) Receiver audio is muted. Refer to receiver manual.
2) Receiver audio output is disconnected or cable is defective
or mis-wired.
3) Sound system or recorder input is turned down.
DISTORTED SOUND 1) Transmitter gain (audio level) is too high. Speak or sing into the
transmitter and check mod level lamps on the receiver (see
Operating Instructions.)
2) Receiver output may be mis-matched with the sound system
or recorder input.
3) Excessive wind noise or breath “pops.”
HISS AND NOISE -- AUDIBLE DROPOUTS 1) Transmitter gain (audio level) too low.
2) Receiver antenna missing or obstructed.
3) Operating range too great.
EXCESSIVE FEEDBACK 1) Transmitter gain (audio level) too high. Check gain adjustment
and/or reduce receiver output level (see Operating Instructions.)
2) Transmitter too close to speaker system.
3) Move transmitter closer to the user’s mouth.

8
SPECIFICATIONS AND FEATURES
Operating frequencies: 150 to 216 MHz
RF Power Output: 50 mW
Deviation: ±15kHz
Spurious Radiation: 50dB below carrier
Frequency Stability: ±0.005%
Equivalent Input Noise: -123dB
Input Sensitivity: 8mV to 1.6V for full modulation
Input Compressor: Soft Compressor; 12dB range
Electret Bias: +5 Volt DC (positive bias)
Antenna: Input cord or microphone body
Input Jacks: Twist-lock micro for electret microphones
Battery Indicator: LED indicates battery condition
Battery Life: Approximately 15 hours
Controls: Power on/off slide switch
Recessed audio gain control
Mute on/off toggle switch (M175-LS only)
Size: 1.3 x 2.35 x 3.7 inches
Weight: 6.6 ozs with battery and microphone
FCC ID: DBZM175 (150 to 172 MHz)
DBZM175A (174 to 216 MHz)
Emission designator: 58K0F3E
Specifications subject to change without notice.

9
Belt Pack Transmitter
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 con-
nection, 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 read-
justment. 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 equipment.
Should any defect develop, Lectrosonics, Inc. will, at our option, repair or replace any
defective parts without charge for either parts or labor. If Lectrosonics, Inc. cannot
correct the defect in your equipment, it will be replaced at no charge with a similar new
item. Lectrosonics, Inc. will pay for the cost of returning your equipment to you.
This warranty applies only to items returned to Lectrosonics, Inc. or an authorized
dealer, shipping costs prepaid, within one year from the date of purchase.
This Limited Warranty is governed by the laws of the State of New Mexico. It states the
entire liablility of Lectrosonics Inc. and the entire remedy of the purchaser for any
breach of warranty as outlined above. NEITHER LECTROSONICS, INC. NOR
ANYONE INVOLVED IN THE PRODUCTION OR DELIVERY OF THE EQUIPMENT
SHALL BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE, CONSEQUENTIAL,
OR INCIDENTAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THIS EQUIPMENT EVEN IF LECTROSONICS, INC. HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. IN NO EVENT SHALL THE LIABILITY OF
LECTROSONICS, INC. EXCEED THE PURCHASE PRICE OF ANY DEFECTIVE
EQUIPMENT.
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
November 1, 2001
LIMITED ONE YEAR WARRANTY