Department of Speech and Hearing Science

Alerting/Signaling Devices

Alerting/Signaling devices alert users to sounds or situations that they may not otherwise hear. These devices are very important for safety, security and convenience. Individuals with all degrees of hearing loss will find alerting/signaling devices to be useful. These devices are designed for both residential use and commercial use including hotels/motels. It is important that the ability to hear or detect a signal be considered not only under ideal circumstances but also under adverse conditions when other sounds are present, from a distance or when the person is asleep and the hearing aids are removed.

Sounds that Can Be Monitored

Device-to-person signaling
e.g. Telephone/TTY, doorbell/door knock, alarm clock, timers, fire/smoke alarm, security systems, appliances, etc.

Person-to-person signaling
e.g. Baby cry, paging of a person from another room or outside. Sophisticated office communication systems are available to send and receive visual messages between secretary and boss, or other co-workers.

Alerting Modes

An alerting/signaling device will alert a person to a sound or situation by utilizing one or more alerting modes.

Auditory
Alerts user to a sound by making it louder, lower in pitch or by bringing it closer to the listener.

Visual
Alerts user to a sound by flashing a bright light or strobe

Vibrotactile
Alerts user to a sound by activating a vibrating device that may be body-worn or placed under a pillow or bed mattress

Types of Sound Detection

Alerting/Signaling devices monitor a sound either by direct electrical connection or by a microphone pick-up. Examples of direct connection include plugging directly into a modular phone jack or hardwiring to an existing doorbell chime. Devices that use a microphone pick-up need to be placed as close to the sound source as possible and can be adjusted for sensitivity. This method must be used when monitoring sounds such as a baby's cry. False signals triggered by undesired sounds pose a problem for microphone activated devices and are more effectively minimized by using a direct connect method.

Types of Signal Transmission

Some alerting/signaling devices are hard wired and alert the user only in the location where it is placed close to or directly connected to the sound source. Other devices or systems are wireless and capable of alerting the user throughout different rooms in a home. Wireless systems utilize one or more transmitters and receivers and send a "wireless" signal by using either a FM line carrier signal or a FM airborne signal transmission. Alerting/signaling devices may also be either single function devices or multi-function devices. Single function devices signal only one type of sound source such as the phone/TTY or doorbell. Multi-function devices or systems are capable of signaling two or more sound sources.