Four Questions for Jim Toal

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Vishay Optoelectronics is a major supplier of infrared emitters, photo detectors, and optical sensors to automotive, consumer, and industrial manufacturers. Vishay also offers a broad selection of passive and active components. Residential Systems interviewed Vishay’s senior manager of product marketing, Jim Toal, about this company wireless speaker technology.

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Edifier’s Rainbow Wireless Speaker System

What exactly is a diffused infrared solution for wireless loudspeakers?
There are two main types of infrared transmissions: direct line-of-sight and diffused. Direct infrared is characterized by the need for an unobstructed line-of-sight between the transmitting and receiving devices. TV Remote control units and IrDA-based technology fall into this category. Diffused infrared is non-line-of-sight and nondirectional. It acts very much like light emitted from an incandescent bulb.

What are the advantages of diffused infrared as a wireless audio solution?
High-quality digital audio transmission requires a bandwidth of 1.4112 Mbit/s for an uncompressed stereo (L/R) source of 44.1 kHz/16 bit CD-quality audio. The Bluetooth bandwidth of one Mbit/s is thus insufficient, and although Wi-Fi has a bandwidth of 11 to 54 Mbit/s, it has several problems, the most significant of which is delayed transmission. Diffused infrared communication can support data rates up to 25 Mbit/s in half-duplex mode. This high bit rate allows the simultaneous delivery of up to four uncompressed, pulse code modulated (PCM) digital audio channels. Where sound and video could be out of sync with RF transmission, diffused infrared employs enough bandwidth to use forward error correction (FEC), which allows the receiver to detect and correct sporadic errors without the need for retransmission.

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Can you reveal any of the manufacturing partners that you are or will be working with in the home theater market?
In the home theater market, our main customer is Infra-Com. One of Infra-Com’s customers for diffused infrared is Edifier, which is the leading supplier of genuine wood enclosure speaker systems in China. They market a diffused infrared system called the Rainbow Wireless Speaker System that won the CES Innovations Award.

What are your technology goals for the home theater market?
With LCD TVs becoming thinner and thinner, it will become nearly impossible to have a “high-def” speaker system integrated into an HDTV. TV manufacturers will pull out the speakers and bundle sound bars with the TV. Given this, our goal is to increase the intensity of our infrared emitting diodes so that companies like Infra-Com can use fewer emitters or move to a smaller packaged emitter. This will allow, for example, the transmit unit of the Rainbow system to be integrated into the AV receiver or TV and the receiver unit to be integrated into a sound bar. As a step in this direction, we recently introduced the VSLB3940 3-mm emitter that has on-axis intensity 10-percent greater than the larger, 5-mm TSAL6200 emitter in a 40-percent smaller form factor. This is just the first in a series of bulk and surface emitting diodes we plan to release this year.