I recently read some information about a TV listening device for the
hard of hearing. It transmits the television sound by way of an
infra-red beam from a transmitter at the TV to a listening device worn
by the TV viewer.*
The information I read states that the signal is transmitted by "95 KHz
infrared". That didn't look right to me (and I don't mean just the
incorrect capitalization of the "k" for "kilo") so I looked up the
frequency of infra-red radiation and found it to be roughly between 100
GHz and 500 THz. These are, respectively, one million and five BILLION
times higher than the 95 kHz in the information.**
Are they just way off on their figures, or is there something here that
I don't understand? Could the 95 kHz be a frequency at which the much
higher frequency infra-red waves are modulated or something? Anybody
have any ideas on this?
Regards,
Bill Hooper
* Apparently U.S. federal law will be requiring movie theaters to
transmit these infra-red signals, too, so the owner of this device may
take it to the theater and use it to hear the sound track of the movie.
** The relationships are:
100 GHz = 100 000 000 kHz
500 THz = 500 000 000 000 kHz
compared to 95 kHz (approx. 100 kHz).
