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The LT-84 ListenIR 2-channel transmitter-radiator (Pat. 9,712,246) from Listen Technologies provides venues, businesses, government agencies, and more with an affordable and easy-to-use assistive listening solution.

Offering twice the IR power and up to six times the coverage area of similar products, the LT-84 can transmit a clear, reliable signal across 2,787 square meters (30,000 square feet). This signal range ensures that users in any mid-sized space, from the boardroom to the courtroom and beyond, enjoy an uninterrupted audio performance.

The LT-84 is also the first infrared assistive listening system to feature expansion radiators (LA-141), which provide delay compensation to ensure that there are no signal cancellation dropouts. Up to four (4) expansion radiators (LA-141) can be added to the system to offer additional coverage (when mounted within 30.48 m [100 ft.] from the unit).

In addition, the LT-84 is the only two-channel transmitter-radiator that can transmit on up to four different frequencies (2.3 MHz, 2.8 MHz, 3.3 MHz, or 3.8 MHz). This flexibility in the field makes setup and operation even easier, while also eliminating the need to purchase separate, frequency-specific transmitter-radiator units.

With the included mounting hardware, and the flexible frequency selection and input connectivity, the LT-84 is an ideal way to add infrared assistive listening capabilities and ADA compliance to your business or venue.


One (1) LT-84 ListenIR 2-Channel Transmitter/Radiator Combo
One (1) LA-210 12 VDC Universal Power Supply/Power Cord
One (1) LA-344 Flexible Mounting Hardware
Two (2) Phoenix Type Connectors
One (1) LA-303 Multi-Lingual Assistive Listening Notification Sign
One (1) Quick Start Guide


  • Affordable, effective, and expandable solution ideal for small to mid-size spaces such as classrooms, courtrooms, boardrooms, and more
  • Multiple frequency options offer additional flexibility and simplicity during installation and setup
  • Offers gapless coverage up to 2,787 square meters (30,000 square feet)
  • Can be expanded with up to four (4) LA-141 expansion radiators for additional coverage area
  • One-cable design utilizes a single CAT-5e to carry both power and signal to LA-141 expansion radiators
  • Multiple input options for easier setup and operation
Configurations & Architectural Specs


  • LT-84-01 ListenIR Transmitter/Radiator Combo (North America)
  • LT-84-02 ListenIR Transmitter/Radiator Combo (Asia, UK)
  • LT-84-03 ListenIR Transmitter/Radiator Combo (Euro)
  • LT-84-04 ListenIR Transmitter/Radiator Combo (Australia)

Architectural Specs

The Infrared Transmitter/Radiator Combo shall be capable of broadcasting up to two (2) audio channels with the choice of four (4) mono carrier frequencies; 2.3, 2.8, 3.3 and 3.8 MHz. Channel carrier selections shall be set via a back panel rotary switches.  The Transmitter/Radiator coverage area shall be up to 30,000 ft² (2787 m²) with LR-4200-IR/LR-5200-IR receivers or 7,500 ft² (697 m²) with LR-42/LR-44 receivers in single channel mode.  The device shall have a timer that shuts off the carriers after 15 minutes when no audio is present at the inputs. The Transmitter/Radiator shall have a SNR of 60 dB or better and THD of less than 2%. The device shall have an audio frequency response of 63 Hz to 15 kHz, +/- 3db.  The device shall have two (2) independent mixing audio inputs, one for each transmission channel. Each mixing input shall consist of one (1) 3.5 mm Microphone input, one (1) balanced Phoenix type input and one (1) unbalanced RCA stereo summing input. The device shall have independent channel audio processing with Limiting, Compression and Noise Gate as well as transmit level control and level indication via two (2) LEDs.  The Transmitter/Radiator shall provide Power and RF signal for up to Four (4) Expansion Radiators over a single CAT-5e cable. The LT-84 is specified.

CAD file(s)

Product Specifications


Frequency Response20 Hz - 20 kHz (+/- 1 dB) Line Input63 Hz - 15 kHz (+/- 3 dB) System Specification (wireless end-to-end with LR-44)
Signal-to-Noise Ratio> 70 dB (SNR) Line Input> 60 dB (SNR) System Specification (wireless end-to-end with LR-44)
Microphone InputTwo (2) 3.5 mm (0.14 in.) Tip/Sleeve connector, -30 dBu nominal input, +14 dB headroom, impedance 4.4k Ohms, 5 VDC bias supply
Total Harmonic Distortion< 0.1% (THD) Line Input< 2% (THD) System Specification (wireless end-to-end with LR-44)
Unbalanced Line InputStereo/Mono Input. Two (2) Dual (RCA) Phono connectors, unbalanced, -10 dBu nominal input, +14 dB headroom, impedance 10k Ohms
Balanced Line InputMono Input. Two (2) Phoenix Type connector, balanced, + 4 dBu nominal input, +14 dB headroom, impedance 100k Ohms


Power SwitchThree (3) position switch - Power OFF, Power ON-Indicator Lights OFF, Power ON-Indicator Lights ON
Carrier Frequency SelectionTwo (2), four (4) position rotary switches (2.3 MHz, 2.8 MHz, 3.3 MHz, 3.8 MHz)
Level Control KnobTwo (2) audio taper rotary potentiometer, counter-clockwise decreases input mix level, clockwise increases input mix level


Power Supply LEDGreen LED on in-line power supply indicates AC power is applied
Audio Level IndicatorsTwo (2) Green LEDs, two (2) Red LEDs, Green LED indicates Audio presence and Red LED indicates peaks in the audio
RJ-45 Amber LEDSolid Amber indicates carrier is present and IR is being transmitted
RJ-45 Green LEDSolid Green indicates power is applied to unit, flashing indicates unit has entered power save mode


Carrier Frequencies2.3 MHz, 2.8 MHz, 3.3 MHz, 3.8 MHz, Selectable
Number of ChannelsTwo (2) channels, Selectable carrier frequency
Frequency Accuracy+/- .005% stability 0 to 50 °C
Transmitter Stability50 PPM
ModulationFM Wideband, ±50kHz deviation max, 50 ?S pre-emphasis
Power Save ModeCarrier will shut off when no audio is present for 15 minutes on both channels to preserve radiator life
Expansion Link OutputTwo (2) RJ-45 connectors - Provides RF Signal and Power, CAT-5e cable 24 AWG, 100 ft. maximum cable length, two (2) LA-141s per output connector


Coverage Area2,787 m² (30,000 ft²) single channel with LR-4200-IR/LR-5200-IR receivers or 697 m² (7,500 ft²) single channel with LR-42/LR-44 receivers
IR Emitter Power1.49 W


Power Supply Input100-240 VAC, 50-60 Hz
Power Supply Output12 VDC, 4 A, 48 W
Power Supply Connector2.5 mm ID barrel connector, center positive
Power OutputTwo (2) RJ-45 connectors. providing Power and RF signal for up to two (2) LA-141 expansion radiators on each output
Power Supply TypeIn-line switching mode power supply, Listen part number LA-210
Power Supply Line CordIEC line cord, North America Type B (LT-84-01), Asia and UK Type G (LT-84-02), Euro Type C (LT-84-03), Australia Type I (LT-84-04)


ColorBlack with White Silk Screening
Unit Weight with Power Supply1.8 lbs. (0.8 kg)
Shipping Weight3.4 lbs. (1.54 kg)
MountingCan be mounted on a wall, ceiling, or table with provided hardware (screws and hollow wall anchors not provided). Optional LA-347 Wall Box Mounting Plate is available for mounting to a standard single gang electrical box.
Dimensions (H x W x D)1.5 x 10.7 x 4.1 in. (3.81 x 27.2 x 10.5 cm)
Unit Weight0.8 lbs. (0.4 kg)


Temperature - Operation14 °F (-10 °C) to +104 °F (40 °C)
Temperature - Storage-4 °F (-20 °C) to +122 °F (50 °C)
Relative Humidity0 to 95% relative humidity, non-condensing


StandardsFCC part 15, ICS-03, CE, UL, CUL, C-Tick, CCC, PSE, KC, GS, RoHS, WEEE
Power Supply Compliance MarksCUL, UL, CE, CCC, C-Tick, KC, PSE, GS, FCC, RoHS
Used With
QCan the LT-84 be remote powered?
AYes. Please reference the "LT-84 Remote Power" Tech Note on the Support Info tab for detailed instructions.
QHow many channels (carriers) can the LT-84 produce?
ATwo (2) channels.
QHow many channels (carriers) can be produced simultaneously in a room?
AFour (4) channels. You will need two (2) LT-84 (2 carriers per LT-84).
QWhat is the coverage area provided by the LT-84?
A30,000 ft² (2787 m²) single channel with LR-4200-IR/LR-5200-IR receivers or 7,500 ft² (697 m²) single channel with LR-42/LR-44 receivers
QDoes the number of channels (carriers) affect the coverage area?
AYes, for one (1) channel (carrier), the line-of-sight coverage area is 30,000 ft² (2787 m²) and for two (2) channels (carriers), the line-of-sight coverage area is 15,000 ft² (1394 m²) with LR-4200-IR/LR-5200-IR receivers.
QHow many Expansion Radiators (LA-141) can you use on a system?
AYes, for one (1) channel (carrier), the line-of-sight coverage area is 30,000 ft² (2787 m²) and for two (2) channels (carriers), the line-of-sight coverage area is 15,000 ft² (1394 m²) with LR-4200-IR/LR-5200-IR receivers.
QHow do I connect multiple Expansion Radiators (LA-141)?
AA maximum of two (2) LA-141s can be connected to each Expansion Link output RJ-45 on the LT-84 with a maximum daisy chained CAT-5e cable length of 100 ft. (30.5 m). CAT-5e cable must be at least 24 AWG!
QWhat is the warranty of the LT-84?
AThe LT-84 has a 3-year warranty. Listen Warranty

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