4.2 Videotelephony

Jan-Ingvar Lindström and Leonor Moniz Pereira


Transmitting pictures via the telephone network is an old gimmick. Indeed, it started some 150 years ago when the Scottish inventor Alexander Bain sent his first picture not via the telephone lines (the telephone was not invented until 1876) - but via telegraph lines. He used a technology very much like the one used later by the German physicist Arthur Korn - the father of the modern telefax. Transmitting moving images is a much later issue, because of the much more advanced technology required. The needed transmission capacity - in the order of a hundred megabits per second - has not been possible to obtain, within reasonable economical limits, except for very special applications. Instead, techniques of processing the pictures have been developed, thus allowing for transmission of moving images via ordinary telephone lines. Only a fraction of the information can be transmitted under such circumstances, but with intelligent signal processing moving images of useful quality can be received.

The technology is interesting for many purposes. Not unexpectedly, some groups of people with disabilities are among those who request the facility most urgently. For instance, being able to communicate in Sign Language via the telecommunication network is a dream that is about to come true for deaf people. But, as will be seen below, there are also other applications for video-telephony that can benefit people with disabilities.


In the following, the term 'videotelephony' is used for moving pictures of such a quality, that a real impression of movement occurs. This means, that anything from broadband down to ISDN 2x64 kbit/s - and even non-standardized communication at about 10 kbit/s - is called videocommunication once the transmitted images give an illusion of movement. Consequently, this is true even for images of poor quality (black-white, blurred, jerky etc.). A higher level is videocommunication of such a good quality that can be used for Sign Language telephony. These kinds of devices are called Sign Language Telephones.

European Activities

In Europe, a number of activities are going on which have the aim of investigating the needs and possibilities for videotelephony among people who are disabled or elderly.

Videotelephony is considered to play an important role in the intervention with, and for the independent living of, people with special needs. Videotelephony may be used as a tool for the intervention, enhancement of team work, collaboration, supervision, distant education and for support as well as plain remote communication.

In Europe, more than 20% of the citizens are disabled or elderly - or a combination of both. Just a small fraction, however, have severe loss of function like blindness or deafness etc. The natural way of communication is based upon visual perception. For people who are mentally disabled, speech impaired, hard of hearing, or deaf it is very important to find a substitute or complement to the ordinary telephone which enables them to express or perceive messages at a distance, i.e. to use still picture or moving pictures i.e. videocommunication. Perhaps the most urgent need is to make it possible for deaf people to communicate in Sign Language via the telecommunications network.

Several Advanced Communication Experiments were run under the CEC RACE I programme in which Finland, Germany, Italy, the Netherlands, Portugal and Sweden participated. In the RACE II programme, service provision has been explored by these partners accompanied by Belgium, Ireland, Norway and the United Kingdom.

Some exercises have been strictly national and run by Public Network Operators' laboratories, as for instance in France by the Centre National d'Etudes des Télé-communications (CNET), in the UK by BT, in Norway by Norwegian Telecom and in Sweden by Swedish Telecom/Telia.

A few experiments have been carried out in laboratories but most of them have been field trials.

Some Data

In a field trial in the UK the Public Switched Tele-communications Network (PSTN) was used at a bit rate of 14.4 kbit/s. Germany and Finland have used analogue transmission for images over Cable TV and PSTN for audio. Two experiments have used 2 Mbit/s bit rate: one in Sweden (also including analogue connections) that was based upon a videoconference network, and one in Portugal that was built upon a 2 Mbit/s switched network. One Swedish experiment used 384 kbit/s for remote interpretation in combination with analogue transmission. All others have used ISDN at a bit rate of 2x64 kbit/s.

The experiments used Cathode Ray Tube (CRT) monitors from 12" to 28" diameter with a few exceptions: in France and the Netherlands comparisons were made between 10" and a 20" screens, and in the UK analogue BT experiment a very small (2 1/2") screen was used.

Besides screen dimensions, the parameters used were the Common Intermediate Format (CIF) and QCIF (360 points /288 lines respectively 180 points /144 lines). The frame rate depended upon the information rate and varied between a few frames per second up to 10 - 15 frames per second. Also, the sound transmission took different shares of the transmission capacity. Table 4-4 gives an overview of the experiments.


Safety, Advice and Guidance - SF - CATV/ISDN 2
Training, Health Care - SF - CATV/ISDN 2
Pastoral Care - SF - CATV/ISDN 2
Servicer-Servicer Communication - SF - CATV/ISDN 2
Counselling - P - ISDN 2
Information - P - ISDN 2
Therapy - P - ISDN 2
Health and Social Care - B - CATV
Integrated Service Provision - D - CATV
Mobile Services Support - D - CATV
Health and Social Care - N - ISDN 2

Visual Impairment
Learning - P - ISDN 2

Hearing Impairment and Deafness
Interpersonal Communication - P - ISDN 2
Information - UK - CATV/ISDN/PSTN
Education - UK - CATV/ISDN/PSTN
Interpersonal Communication - UK - CATV/ISDN/PSTN
Interpreter, Comm. + Relay Service - S - ISDN 2 + ISDN 30
Interpersonal Communication - I - ISDN 2
Information - I - ISDN 2
Interpretation - I - ISDN 2
Assistance - I - ISDN 2
Training and Teaching - I - ISDN 2
Audiological and Social Care - I - ISDN 2
Support to Prelingually Deaf People - I - ISDN 2
Remote Interpretation - S - ISDN 6

Intellectual Impairment
Learning - P- ISDN 2
Health and Social Care - N - ISDN 2
Recreation/Leisure - IRL - CATV
Pre-vocation/Vocation Training - IRL - CATV
Support to Service Delivery Staff - IRL - CATV
Development of the Social Network - IRL - CATV
Development of Communication Abilities - IRL - CATV
Interpersonal Communication - S - ISDN 2

(Table 4-4) Overview of some videotelephony experiments in Europe on behalf of people with disabilities.

Trials with Persons who are Deaf or Hard of Hearing

The transmission of moving pictures is a necessity in providing remote communication for people who are prelingually deaf. This is true independent of whether sign language or lip reading - or a combination - is used. The critical question is the picture quality, i.e. the trade-off between contrast, compliance and resolution. In analogue experiments with coaxial cables or when the Cable TV network is used, no problems appear - the communication is swift and unambiguous. For economical reasons, however, the goal has been to use digital transmission at as low bit rates as possible. With the improvement of codec technology it seems that ISDN 2, i.e. 2x64 kbit/s will be sufficient for sign language as well as lip reading.

A special and very interesting application is remote sign language interpretation. Instead of calling for an inter-preter to come to a certain place, a video connection can be established and the interpretation made via video-communication. This reduces travelling and delay time tremendously.

Support for Persons with Mental Disabilities

Many people with a mental disability have problems using ordinary telephones. There are several reasons for this. One is limited verbal skills. Another is the lack of visual support to the spoken message - to see who is talking or to see objects which are referred to. Videotelephony may help overcome these problems. At some experimental sites specially developed concept keyboards have proved to be very useful in combination with multimedia terminals.

Other Disabilities

Other groups of people with disabilities have been shown to benefit from videotelephony. One example would be people with brain injuries, who may need to express themselves in different ways. Also, people who are speech impaired may find videotelephones useful, and trials have been carried out on behalf of people with aphasia.

More astonishing perhaps is the fact that visually disabled people can benefit from videotelephony. One example is to use the technique as a "remote eye" in the sense that objects, forms, printed matters etc. can be shown to sighted people via videotelephony and identified and described verbally to the blind person.

In one experiment videotelephony has been used suc-cessfully as a tool for the remote education of partially sighted (and slightly mentally disabled) school children.

Elderly Persons' Communication

Videotelephony services for elderly and fragile people have been tried at a few sites. In these cases rather high picture quality has been utilized and presented much like pictures on a home TV. The applications have much in common with an emergency telephone system, but allow for much more versatile communication.

Results and Prospects

The goal of these experiments has been to explore the pros and cons of videotelephony on behalf of people with disabilities. Essential factors have been:

- technical aspects, i.e. functions versus bit rates;
- design of the sites, i.e. necessary auxiliary equipment and layout of components;
- social and pedagogical considerations, i.e. the fulfilment of the communication and service goals.

The experiences so far show that:

- remote communication based upon gestures or graphics is possible with current technology, although available codecs for 2x64 kbit/s sometimes hamper Sign Language communication;
- videocommunication can support, enhance or replace telephone communication for groups who have difficulties using ordinary stand alone telephones, e.g. people with mental disabilities;
- participation in daily activities at school and at work can be improved by videotelephony;
- intervention by various specialists can be facilitated as videotelephony can replace travelling to clients;
- human resources can be better managed, so that more service facilities can be provided to institutions, a person's home etc.;

- videotelephony seems to support and develop good communication during the experiments between teachers, parents, psychologists, technical experts and the clients.


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