FM Listening Systems broadcast the speaker’s voice directly to the ears of individual listeners. While the speaker wears a compact transmitter and microphone, listeners use portable receivers and earphones to hear the presentation clearly and easily, even from the back of the room. This transmission happens on reserved radio spectrum 216-217 MHz. Single-channel and multi-channel systems are available. They provide a strong and reliable signal, which is able to pass through walls and opaque objects. They even work well in the open air. Ideal for large areas such as houses of worship, classrooms, auditoriums, etc.

RADIO FREQUENCY vs. INFRARED TRANSMISSION

Radio Frequency also provides a strong and reliable signal, which is able to pass through walls and opaque objects, and works well in the open air. Radio frequency receivers consume more electrical power than the infrared type; therefore battery life is considerably shortened. Finally, with the advent of digital electronics and signaling, infrared has taken the lead with regard to component features -- a lead which is being diminished by some of the new models of radio frequency transmission systems.

With Infrared systems, transmission is confined within opaque walls, making it a good choice for movie theaters, boardrooms, and courtrooms - anywhere privacy is valued. Infrared systems are also immune to radio interference. Receiver management is easier with infrared systems because there is no reason to search for the frequency. However, infrared is usually not appropriate for outdoor use because sunlight generates interference. Power consumption is also quite considerable, however digital electronics offer a wider array of features, in particular auto shut-off mode. Channel capacity is approximately 5 times that of RF. In general, infrared systems are more costly and require more equipment to cover a larger area. (Source: Audio Links)

WIRELOOP SYSTEMS

Loop technology consists of a thin 'loop' wire that is placed around the listening area, a special amplifier and microphone(s). Speech signals are amplified and circulated through the loop wire. The resulting magnetic energy field is picked up and amplified by the 'telecoil' (or telephone switch circuitry) found in many hearing aids, cochlear implants and induction loop receivers.

WHAT IS A NECKLOOP?

A neckloop plugs into a receiver earphone jack to provide a magnetic signal that can be picked up by a hearing aid equipped with a telecoil (t-switch). It is worn like a lanyard.