Lectrosonics SR175 User Manual
SR175
COMPACT RECEIVER
OPERATING INSTRUCTIONS
and trouble-shooting guide
Digital Code Squelch
LECTROSONICS, INC.
Rio Rancho, NM
INTRODUCTION
The SR175 is a fixed frequency, crystal controlled receiver designed for use in public address
applications. A proprietary Digital Code Squelch* is used in the system design to eliminate squelching
problems caused by interference. The compact size of the receiver permits mounting the receiver
almost anywhere. The audio output is a balanced XLR type, variable in level, to match any type of
sound system.
The digital code system provides much more reliable control over the receiver audio output than a
conventional squelch can provide. The matching 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 SR175 circuitry utilizes the latest surface mount technology, with significant oscillator shielding. Up
to four systems can be operated simultaneously in close proximity in the 169 to 172 MHz band without
intermodulation, crosstalk or squelch problems. The housing is a durable aluminum extrusion with
rugged connectors for lasting reliability.
TABLE OF CONTENTS
INTRODUCTION .......................................... 1
RECEIVER FRONT PANEL ................................... 2
RECEIVER REAR PANEL .................................... 3
SYSTEM SETUP AND OPERATION ............................ 4
INDICATORS ............................................. 4
ANTENNA USE AND PLACEMENT ............................. 5
TROUBLESHOOTING ....................................... 6
REPLACEMENT PARTS and ACCESSORIES ..................... 6
SERVICE AND REPAIR ..................................... 7
RETURNING UNITS FOR REPAIR ............................. 7
SR175 SPECIFICATIONS AND FEATURES ....................... 8
WARRANTY ....................................... Back cover
1
RECEIVER FRONT PANEL
OUTPUT
POWER
LECTROSONICS
SR175
LEVEL LIMIT CODE
DIGITAL
CODE
OFF ON
LEVEL and LIMIT LEDs - Indicates the modulation (audio level) of the incoming signal - see
transmitter manual for proper adjustment of transmitter "MIC LEVEL" or "GAIN." The LEVEL lamp
should flicker, or stay lit as you speak into the microphone. The LIMIT lamp is a "peak" indicator
showing that the audio level in the transmitter is being limited. It is normal to see an occasional flicker
of the LIMIT lamp.
POWER OFF-ON Switch - This slide switch turns the power off and on.
POWER LED - Glows when the switch is in the "ON" position and the power source is good, or when
the AC adapter is properly connected. If this LED is very dim or does not light up when the switch is
turned on, check the power source.
CODE LED - Lights when the transmitter is turned on and the internal code in the transmitter matches
this particular receiver. If the receiver is turned on after the transmitter, the code led will not come on.
In this case, it will be necessary to turn the transmitter off and back on to enable the receiver. When
the carrier signal from the transmitter is too weak to produce a clean audio signal the receiver will
squelch (no audio) but the code lamp will remain lit.
OUTPUT - An attenuator used to regulate the output level of the receiver. When fully counterclockwise, the output of the XLR jack on the rear panel will be the same as a typical microphone. Fully
clockwise, the output level will be similar to a high output electret microphone. Intermediate settings
are often necessary to ideally match the level with other equipment.
Figure 1 -SR175 Front Panel
2
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