In modern society, independent travel is a prerequisite to successful education and employment. For blind persons, independent travel involves not only finding a safe path through the environment, but being able to find landmarks and orient oneself. For blind persons, these tasks are challenging and have been the subject of many efforts to develop assistive technology to make some or all aspects of travel easier. Technology to assist blind travelers can conveniently be categorized as Mobility devices and Orientation devices. The following is a summary of these developments.

Mobility Devices
Historically, most efforts focused on the mobility part of the problem – helping the blind traveler to detect objects, hazards and boundaries in, near or alongside his path, avoid collisions, and steer a straight and safe course through the immediate environment. A family of mobility aids known as Electronic Travel Aids or ETAs has resulted. These vary from simple obstacle detectors to more complex environmental sensors. For example, the Mowat Sensor is a hand-held ultrasonic device that uses a vibratory code to warn of the presence and range of an object in its beam. At the other end of the spectrum is the head worn Sonicguide, which processes broad band ultrasonic reflections so that the pitch of the received signal indicates range, the timbre indicates the nature of the target, and the inter-aural amplitude difference indicates direction. The Laser Cane uses laser beams to detect objects, and incorporates the ability to warn of drop-offs. Another mobility aid is the Sonic Pathfinder, the subject of another paper in this issue.

Orientation and Navigation Devices
Technology to address the broader orientation and navigation aspect of the Orientation and Mobility (O&M) problem has a shorter history, and devices in this category have only recently entered commercial production. The infrared Talking Signs system reported on here was developed as an environmental labeling system to allow blind travelers to locate and identify landmarks, signs, and facilities of interest in the environment. It uses speech messages stored in infrared transmitters as labels, and the user’s hand held receiver converts the transmissions back into speech. The infrared beam pattern provides control of range and coverage, and the directional nature of infrared light allows the user to accurately locate each sign.

Since this concept was put forward in 1979, a number of other technologies have been proposed for the orientation problem, though only infrared signage systems are currently available. The Sonic Orientation and Navigation Aid (SONA), a prototype environmental labeling system with sound sources triggered by a garage door opener transmitter was developed by the Veteran’s Administration concurrently with Talking Signs. Variants of this concept using speech labels triggered by a user carried device include the REACT system, The Open University device, and the Acrontech International system.

A number of systems using radio transmission of speech messages to receivers carried by the user have been proposed. Verbal Landmark® demonstrated a system in 1993 in which a portable receiver detects messages transmitted from an electromagnetic loop. The Fanmark "Locator", advertised in 1993, employed consumer receivers to pick up digitally recorded voice messages on an unused FM band. A proposed Chico system would use transceivers triggered by a user-carried speech output transceiver. A proposed NYNEX system would employ a "grid" of radio frequency transmitters located on tall structures and street corners, to which the user would orient and triangulate using a directional receiver and headphones.

Several projects have explored GPS applications for assisting orientation. Loomis has systematically studied this possibility combined with externalized sounds for locating environmental features. A derivative of this approach has been developed by Arkenstone Inc. whose prototype used a notebook computer packaged with the GPS and synthetic speech in a backpack. This technology has been further developed and brought to the market by Sendero Group, LLD under the name “GPS-Talk”. The RNIB MoBIC (Mobility of Blind and Elderly People Interacting with Computers) project (1994-96) recommended GPS technology and proposed a protocol, based upon ISO’s Open Systems Interconnection architecture (1978), to interface different technologies that could be used for orientation and navigation.

Besides Talking Signs® the remote infrared signage system (RIAS), described in detail on this site , An infrared system (“Pathfinder,” modeled on the Talking SignsR system) has been evaluated in a London subway station. The OPEN (Orientation by Personal Electronic Navigation) project set out to investigate the feasibility of a “networked” multilingual system of infrared transmitting signs (1994) incorporating real time information for subway applications. More recently, a signage system consisting of beacons activiated by transmitters carried by users has been installed in the Czech Republic.

Intersection-Specific Technology
Accessible Traffic Signal systems are gaining prominence with at least eleven products readily available to cities. These devices variously provide information about the light cycle; the street name and direction of travel; street geometry; location of the pedestrian crossing actuator; and location of the opposite corner. Devices can be audible, using speaker or infrared transmission (link to intersection paper, NIDRR 1) to communicate by way of spoken messages, tones or other unique sounds. Other devices are tactile with either raised lines to communicate properties of the intersection or vibrators to indicate the light cycle. Perhaps the greatest improvement in the traditional audible speaker system is circuitry which automatically adjusts the output volume depending upon the ambient sound level.

Citations:
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