Compatible with a wide range of transmitters, the LR-42 stethoscope receiver from Listen Technologies gives venues a reliable and user-friendly receiver option. Each unit can use either AAA alkaline or NiMH rechargeable batteries, providing users with up to 30 hours of clear, reliable audio performance. The built-in auto shutoff feature helps to extend that battery life by turning the unit off after 30 minutes of not receiving an audio signal.

The LR-42 stethoscope receiver is capable of receiving up to four (4) channels of audio in either mono or stereo, making it a compact and reliable solution for assistive listening needs including language interpretation, live theater, houses of worship, courtrooms, and a wide range of other venues.


One (1) LR-42 IR Stethoscope 4-Channel Receiver
One (1) LA-152 IR Receiver Battery Compartment (Non-Charging)
One (1) Quick Reference Card


  • Secure and reliable infrared audio for applications where isolated signals or security is a matter of importance
  • Stylish, all-in-one stethoscope design makes each unit easy to wear and easy to use
  • Receives up to four (4) channels of crystal-clear audio in either stereo or mono
  • Compatible with standard AAA alkaline or NiMH rechargeable batteries for up to 30 hours of listening
  • Auto shutoff feature extends battery life by powering the receiver off after 30 minutes
  • Comfortable, replaceable ear pieces for easy cleaning and maintenance
Configurations & Architectural Specs

Architectural Specs

The stethoscope IR receiver shall be capable of receiving on four (4) carriers (2.3, 2.8, 3.3, 3.8 MHz) and the channel shall be displayed on one (1) of four (4) front panel LEDs. The receiver shall be capable of being locked on a channel. The receiver shall be capable of receiving a stereo signal on each of the four carriers. The receiver shall have a SNR of 60 dB or greater and have built in squelch control. The device shall have an audio frequency response of 63 Hz to 15 kHz, +/- 3db and shall have distortion of less than 2%. The device shall operate for 30 hours with two (2) AAA alkaline batteries and 15 hours with two (2) AAA NiMH rechargeable batteries. The LR-42 is specified.

Product Specifications
Specification LR-42


Frequency Response 63 Hz - 15 kHz (+/- 3 dB)
Signal-to-Noise Ratio Mono: > 60 dBStereo: > 52 dB
System Distortion < 2% total harmonic distortion (THD)
Audio Output Jacks Built in Stethoscope speakers
Audio Output Power 20 mW maximum at 32 ohms


User Controls Volume, Power, Channel Select
Programming Channel Lock, Auto Seek, Channel Lock-Out, Squelch


Unit Power Indicated by current channel selection LED
Channel Selection Red LED illuminates on the current channel selection


Carrier Frequencies 2.3 MHz, 2.8 MHz, 3.3 MHz, 3.8 MHz
Number of Channels Four (4) selectable channels
IR Detectors Two (2) detectors under front IR lens
Sensitivity One (1) nW/cm2 at 40 db SNR
Frequency Accuracy +/- .005% stability 0 to 50C
Squelch Automatic on loss of RF signal (40 dB SNR)


Battery Type Two (2) AAA alkaline batteries or NiMH battery pack
Battery Life 30 hours alkaline, 15 hours NiMH rechargeable pack (LA-364)
Battery Charging Time Fully Automatic with NiMH battery pack and LA-350 charger


Width 4.00 in. (102 mm)
Height 1.80 in. (46 mm)
Depth .75 in. (19 mm)
Length Stethoscope Arm length 8 in. (203 mm)
Color Dark Grey with White Silk Screening
Unit Weight with Batteries 2.95 oz. (85 g)
Shipping Weight 1.0 lb. (0.5 kg)
Weight 2.15 oz. (60 g)


Temperature - Operation 14 ?F (-10 ?C) to 104 ?F (+40 ?C)
Temperature - Storage -4 ?F (-20 ?C) to (122 ?F)
Relative Humidity 0 to 95% relative humidity, non-condensing


Standards FCC Part 15, Industry Canada, CE, RoHS
Used With
Q How does the receiver know if the signal is mono or stereo?
A It automatically detects the type of signal and responds accordingly.
Q My stereo signals are a bit noisy. How can I resolve this problem?
A Add more radiators. When you are transmitting stereo signals, the signal is degraded slightly. Increasing your radiator coverage will help mitigate this.
Q What happens when there is no signal from the radiators?
A The receiver’s audio signal is muted and after 30 minutes the unit automatically shuts down to conserve battery life.
Q How does the user select carriers?
A By pressing the SELECT button on the front of the receiver.
Q Can the receiver automatically find a carrier?
A Yes, it will automatically seek and find all available carriers when the power is turned on. If no carrier is found, the unit will stop on the last used channel.
Q Can I use a mono or stereo headphone with the LR-44?
A Yes.
Q How many receivers can be used in a system?
A Infinite number - there is no limit.
Q How do you replace the batteries in the receiver?
A For non-rechargeable batteries (AAA alkaline), remove the battery compartment and replace the batteries with fresh AAA alkaline batteries. For rechargeable NiMH batteries, simply replace the sealed battery pack with a freshly charged pack.
Q How do I recharge the NiMH batteries?
A Use the Listen LA-350 8-Unit Charging/Storage unit. This unit will charge batteries that are in receivers or out of receivers.
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