Technology for Persons with Hearing Impairment:

Telecommunication & Alerting Devices

Telecommunication Devices for the Deaf

There are two basic difficulties between people who are hard of hearing and those who cannot understand speech (deaf) when it comes to using telecommunication devices. First, the sound quality is not always the best when conveyed over telephone lines. You may have noticed some high pitched hissing, possibly some background noises (including muffled communication from another person's call), static or distorted voice quality when you are using the phone. When a person has a hearing impairment, these sounds tend to exaggerate the effect of the hearing impairment by the distorting overall quality of any sounds. Second, phone conversations lack the face-to-face quality of in person communication. This hinders someone who is having trouble with hearing sounds from being able to use facial cues to "fill in" the missing content. They cannot rely on facial expression, gestures, and sometimes lip reading as aids to understanding spoken communication. This is where telecommunication devices fulfill an important role for persons with hearing impairments or deafness.

Amplification Devices

The first type of telecommunication device would be an amplification device. As the name implies, amplification devices take the normal auditory signal and boost the level overall or, in some instances, boost selective frequencies (usually low or high) to match the person's hearing profile. Most amplification devices can be fitted over the earpiece of the phone, are integrated into the standard handset, or can be attached to the phone through modular wiring. Regardless, these devices work with the standard telecommunication technology and require little, if any, modifications. For that reason, they are a very flexible, inexpensive, and convenient type of ALD for many persons with hearing impairment.

The three most common types of amplification devices for the person with a hearing impairment who wants to use the standard phone are:

 Amplified Headsets  Modular Amplifiers  Portable Amplifiers

Amplified Handsets

You are probably most familiar with this type of amplifier. Many public telephones have a handset with an adjustable volume control on the inside of the handle. This allows the user to adjust the sound from normal volume all the way to a 30 dB (decibel) increase. All amplified handsets must be connected to a modularized phone system. Often, to avoid

1 incompatibility, these handsets must be connected to a phone of the same make and model. To review a few amplified phones, click on the links below.

Phone Amplification Devices

Amplified Phone (mild hearing loss)

Amplified Ringer

Modular Amplifiers

The modular amplifier can be attached to most phones and will perform the same function that the amplified handset does - that is, amplifies the sound. Modular amplifiers are typically attached between the handset and the base phone unit. Some units allow the user to adjust the level of amplification; others (usually the less expensive models) allow only one level of amplification. These modular amplifiers can only be attached to modular phones (not cell phones, portable phones, etc.). Some modular amplifiers have difficulties with different types of phones so you need to check for compatibility before purchasing one of these devices.

To learn more about modular amplifier products:

Phone Amplification Devices

Portable Amplifiers

Portable Amplifiers are small, detachable amplifiers that attach to the telephone handset fitting over the earpiece. These devices intercept the sound signal leaving the handset and boost that signal and/or convert the signal to electromagnetic signals that the hearing aid's telecoil can accept. Portable amplifiers can be used in conjunction with a hearing aid or apart from one.

Examples of Portable Amplifiers:

Portable Amplifier

2 Telecommunication Devices for the Deaf

The second category of devices for telecommunication access is telecommunication devices for the deaf (TTY or TDD).

What is a TTY?

TTYs (or Teletypewriters - TDDs as they are now called) use text to communicate over standard telephone lines. The TTY unit itself converts auditory tones into text characters that are then displayed as a text message. To work, a TTY must be communicating with another TTY. The person sending the message types his or her message into the TTY device on their end. Their TTY converts the keystrokes into auditory tones that are similar to the tones you hear when you dial a telephone number. These tones are sent across the voice telephone lines to the receiving TTY. This TTY accepts the auditory tones and converts them into characters and displays these on the text display or prints them onto a printer (if included in the TTY).

Even though TTYs come in a variety of shapes, sizes, and have different functions, they generally have similar components:

Over time TTY users have developed an etiquette for conversations to alert each other when the person is finished with their comment, statement, question (the user types GA and the end of their message - "Go Ahead"), when one person has completed the call (the user types SK - "Stop Keying") and when the conversation is complete and the connection can be broken (SK, SK).

All TTYs use half-duplex communication schemes. That is, only one TDD can be sending information at a time. This creates longer telephone conversations. In addition, since most TDDs use a 5 bit data transmission process (and computers use an 8-bit process), special software is required to insure that TDDs and computer are able to communicate with one another.

Frequently Asked Questions About TTY or TDDs

Telephone Relay Services

Currently, all states are operating telephone relay services that allow a user with a TDD to communicate with persons or businesses that do not have these devices. All relay services are subsidized by a small fee included in standard phone line services.

What is a telephone relay service?

3 Alerting Devices

The final type of AT devices for persons with hearing impairment and deafness are alerting devices. An alerting device is any aid or device that alerts a person with a hearing impairment to the environmental sounds that are typically conveyed through auditory means. For example, the auditory sound of a doorbell may not be recognized by a person with a high frequency hearing loss. An alerting device can take that auditory signal, convert the sound into a visual cue (a flashing light), and alert the person that someone has pushed the doorbell.

Because alerting devices help the person to live independently and control their environment, they are sometimes listed under environmental control units (ECUs). The.ECUs we discussed earlier in the Access unit was primarily designed for a person with a physical or cognitive impairment. Alerting devices, on the other hand, are specifically designed for a person with a moderate to profound hearing loss.

Alerting devices can be used full-time in conjunction with a hearing aid or some other form of assisted listening device (ALD), or they may be used only part-time when the user is not using an ALD. Regardless of their pattern of use, all alerting devices do three things:

 Detect and Environmental Sound  Convert the Sound  Signal the Person with a hearing Impairment

Detecting Sounds

Most alerting devices contain a built-in microphone that detects the sound. Some alerting devices, however, are hard wired to the device by a physical connection. In this way, the alerting device becomes part of the original device (doorbell, telephone, etc.) and makes use of the existing circuitry. Regardless of which method the device uses to detect the sound, the alerting device is positioned close to the sound producing device.

Converting the Sound

Alerting devices typically convert the sound to another sensory signal (tactile or visual). Some alerting devices will change the frequency of the auditory signal. For example, a telephone alerting device may convert the high frequency ring to a low frequency buzz to allow a user to use their residual low frequency hearing abilities.

4 Signal the User

All alerting devices will use the alternative sensory channel (tactile, visual, or modified auditory) to alert the user that an auditory signal has been issued. In instances where multiple alerts are possible (fire alarm, telephone, doorbell, baby crying, microwave beep, dryer buzz) the person may use more than one alerting device or use an alerting device that allows them to change the frequency or duration of the modified signal. As an example of this latter situation, a person may have the light flash at a different rate for each of the devices listed above. This allows the person with a hearing impairment to differentiate between multiple devices.

Some examples of alerting devices include:

 sounds converted to visual stimulus o flashing lights, strobe light, colored light on/off  sounds converted into tactile stimulus o vibration, fan, heater  Sound modifications o changing a high frequency sound to a low frequency sound or vice versa

Examples of Specific Alerting Devices:

Clocks and Alarm Systems

Visual Alert Signalers

Loud Phone Ringers

Vibrating Alarm Clocks

Bed Vibrating Alarms

Vibrating or Sound Door Knock Alerts

Vibrating Watches

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