C_S_D 4340 Lecture Notes - Lecture 25: Federal Communications Commission, Electromagnetic Interference, Frequency Modulation
Document Summary
Assistive technology for the hearing impaired, continued 3. Federal communications commission: 72 mhz-76 mhz used for listening devices, commercial usually 88 mhz to 108 mhz, interference. Although the 72-76 mhz. band was allotted as the auditory frequency band, there is a potential for outside interference. Certain paging systems and fire call boxes may use these frequencies or ones very close to them. If two transmitters on the same frequency are used in close proximity, the receivers will seek the strongest signal. Fm systems are available in narrow band channels which provide a better signal rejection rate. It transmits through walls so adjacent rooms should be equipped with other frequencies to avoid interference. Transmitters range from to ,000 each and receivers from. A typical system costs about ,500: while theoretically, an fm receiver from one manufacturer can be employed with a transmitter made by a different company, the reality is a bit more complex.
