Components: Transmitter and Receiver Systems
Electromagnetic induction loop
Notes:
We have already stated that one of the wonderful characteristics of ALDs is that sound is brought from a distance directly to the ear. But how is this accomplished? Will the sound be sent from the transmitter to the receiver via radio waves, light, or electromagnetic waves? These are the three basic systems that are in use today: FM (radio waves), infrared (light waves) and induction loop (electromagnetic waves). Each of these systems will be discussed in more detail momentarily.
All of the systems have volume control settings that can be adjusted by the individual user, they all help to minimize the effects of poor acoustic conditions in classrooms, and they can be used with public address systems. As you will see, some systems are more appropriate in some settings than others.
These systems have other uses, as well. They are used in foreign language interpretation and with students who have difficulty concentrating due to distractions. The systems have also been used between sighted guides and persons with visual impairments, in activities such as skiing. They are also popping up in our everyday lives in ways that might surprise you.
There are other systems that are commonly called ‘hardwired’ systems. Instead of transmitting signals across great distances through the air, these systems transmit signals across much shorter distances through a connecting wire. These are not typically used in classroom situations so they are not covered here, however they are often used in offices, homes or in the car for one-on-one conversations.