Summary
The maker's design and installation manual for its stationary infrared transmitter and radiator, covering how sunlight, lighting, room surfaces, channel count and emitter ageing affect coverage.
Key findings
- Says its systems use higher modulation frequencies (carriers at 2.3, 2.8, 3.3 and 3.8 MHz) that make them less susceptible to fluorescent lighting, but are not immune to sources of infrared light such as sunlight and plasma displays.
- Explains that infrared is line of sight in open space, while light-coloured, reflective surfaces extend coverage; in a very large room a listener may need to point the receiver at the radiator.
- States that its products work with other makers' systems that use the same carrier frequencies.
- Rates one radiator at about 10,000 sq ft (929 square metres) for one channel with its LR-42 and LR-44 receivers, falling to 5,000 sq ft for two channels and 2,500 sq ft for four, and about 40,000 sq ft for one channel with its LR-4200 and LR-5200 receivers.
- Says radiators are under-rated by 40 percent because emitter output falls by that much after about 8,000 operating hours, so systems should be designed from the published coverage patterns rather than by trial and error.
- Recommends at least two radiators except in small rooms, overlapping coverage, extra radiators for shaded areas such as under balconies, and a delay adjustment where the coverage of radiators overlaps.
- Calls infrared secure and free of radio interference compared with radio transmission.
- The Design Guide, printed p. 7, pairs 5,000 sq ft with 465 m² for two channels and 2,500 sq ft with 232 m² for four channels using LR-42/LR-44 receivers. It pairs 40,000 sq ft with 3,716 m² for one channel using LR-4200-IR/LR-5200-IR receivers. These are the manual’s stated equivalents.
- Printed page 23 lists wireless end-to-end frequency response of 63 Hz-15 kHz ±3 dB, A-weighted signal-to-noise ratio above 60 dB in mono or 52 dB in stereo, and total harmonic distortion below 2%. These are manufacturer system specifications.
- Troubleshooting (printed page 57) identifies noise or distortion near the edge of coverage and interference or noise from windows and sunlight.
Limits
The maker's figures for its own products, without independent measurement; it does not discuss LED lighting. The troubleshooting section does warn that windows and sunlight can cause interference and receiver noise. Date from the file name and the PDF's creation date; the manual itself shows no date.
Read the original
www.listentech.com/wp-content/uploads/2021/10/LT-82-_-LA-140-User-Manual-2022-09-26.pdf
Cited in
- Which hearing devices can receive which systems?Open
- Auracast, hearing loop, infrared, RF or Wi-Fi: which suits which room?Disputed
- How many receivers and neckloops does each code require, and how should a loan pool be run?Partly answered
- Where does infrared assistive listening work, and where does it fall short?Partly answered
- What does each system cost to install and to run over its life?Open
- How good is the sound each system delivers: bandwidth, codecs and speech understanding?Partly answered
Cite this source
Listen Technologies. LT-82 & LA-140 User Manual: Stationary IR Transmitter and Stationary IR Radiator. 26 September 2022. https://www.listentech.com/wp-content/uploads/2021/10/LT-82-_-LA-140-User-Manual-2022-09-26.pdf (accessed 13 October 2026).
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