Friday, January 11, 2013

Infrared audio headphone link for TV

To listen via headphones preferably good ‘surround your ears’ muff-type headphones, which not only deliver the wanted sounds directly to your ears and hearing aid(s) but also cut back the competing sounds at the same time. If you pick the right kind of headphones, with some acoustic damping in the earmuffs, they don’t cause your hearing aid(s) to emit feedback and whistle sounds either.

The result is comfortable listening at a volume level that’s right for you, where you can hear and understand everything that’s being said.

Headphone jack
Some TV sets do have earphone jacks, so you could simply fit a pair of stereo headphones with their own volume control (if necessary), plus a long cord and plug to mate with the jack on the TV. But many sets do not have a headphone jack, and many that do have it wired so that when headphones are plugged in, the speakers are disabled.

That’s fine for you, but no good for everyone else. In any case, being hooked up to the TV via a long cable has its own problems: you can forget to take ’em off when you get up for a comfort break or someone else can trip on the cable when they move about the room.

Friday, January 4, 2013

Ultrasonic Transmitter and Receiver

THE Ultrasonic Transmitter circuit shown in Fig. generates ultrasonic sound waves at a  frequency of 40kHz. The key component is a 555 timer, IC1, which is wired as an astable to produce an output frequency of 40kHz. This stream of electrical signals drives the ultrasonic
transmitter transducer TX1.

Potentiometer VR1, used as a variable resistor, enables you to make fine adjustment to the frequency when setting up the control system to ensure that TX1 is resonating at its optimum natural frequency, thereby ensuring maximum range. This adjustment is described in the ‘synchronising’ section at the end of the receiver section.

ultrasonic transmitter circuit