|The following ITU-R deliverables relates to wireless and broadcasting communication systems for people with disabilities or subject to health hazards:This Handbook provides guidance to engineers responsible for the implementation of digital terrestrial television broadcasting and combines material dealing with digital and analogue television systems and planning aspects of this new topic. This Handbook covers some aspects of Captioning and Closed captioning.
Captioning information, like audio associated with the video, must be synchronized with each television frame. Captioning information should be uniquely identified and carried as user data within the video picture layer. However, the value of using PES packets or sections to maintain commonality in processing at the receiver between captioning and other applications should be considered further.
Closed captioning is a captioning service designed for the hearing impaired. Like general captioning information, closed caption services must be synchronized with each television frame and should be uniquely identified and carried as user data within the video picture layer. However, nothing in the MPEG-2 syntax would prevent closed captioning data being sent in a separate PID, and in some applications this might have some advantage over the carrying the data within the video picture layer. The value of using PES packets or sections to maintain commonality in processing at the receiver between captioning and other applications should be considered further. This Handbook provides guidance to engineers responsible for the implementation of digital terrestrial television broadcasting and combines material dealing with digital and analogue television systems and planning aspects of this new topic.Indicates:
- that many forms of hearing impairment cannot be satisfactorily improved by audio amplification only;
- that a number of means have been used to transfer speech signals to the listenerīs hearing device. These means include infrared radiation, use of the magnetic induction internal to current loops, including operation at audio frequencies, VHF radio and the external induction field of a radiating antenna;
- that Annex 1 contains some information concerning radio system concepts;
- that Annex 2 contains summary system characteristics of radio induction field and VHF systems suitable for wireless hearing aid,
This Recommendation is intended to provide a basis for the derivation and estimation of the values of electromagnetic radiation from a broadcasting station that occurs at particular distances from the transmitter site. Using such information, responsible organizations can then develop appropriate standards that may be used to protect humans from undesirable exposure to harmful radiation. The actual values to be applied in any regulation will naturally depend on decisions reached by responsible health agencies, domestic and worldwide.
- that the technical parameters for radiocommunication systems for persons with impaired hearing should be in accordance with Annexes 1 and 2;
- that the practical application of infrared systems and audio frequency induction loops to communicating with persons with impaired hearing should also be considered for some applications.
Electromagnetic compatibility (EMC) is a general concern for electronic equipment and particularly electronic medical devices. If electromedical devices are used in the presence of strong electromagnetic fields they may malfunction. The risk of such malfunction increases if the field strengths are great enough. The risk of malfunction depends upon several variables, such as the level of field strength, which is dependent on distance between the radiating antenna and the device, the transmitter power, the frequency of the waves, the type of modulation of the radiated signal, the effect of cable coupling as well as the electronic devices own RF immunity.
RF interference to electromedical devices can usually be reduced or eliminated by suitable RF screening or electronic filtering. Applied techniques derived from those commonly used for EMC are suitable. Special limits, that may be significantly lower than general limits for population, may apply to medical devices, implanted or not, and to medical instrumentation.
Extensive studies on the subject of photosensitive epilepsy, which have taken place around the world, have led to formulation of this Recommendation. The guidance proposed in this Recommendation is for the protection of the vulnerable section of the viewing population who have photosensitive epilepsy, and who are therefore prone to seizures triggered by flashing lights, including certain types of flashing television images. Broadcasting organizations are encouraged to raise awareness among programme producers of the risks of creating television image content which may induce photosensitive epileptic seizures in susceptible viewers. Appendices 1 to 5 provide additional information on this subject.Several cases of individual or collective photosensitive epilepsy in vulnerable subjects, in particular children, induced by flickering television images have been reported from various parts of the world. This ITU-R Question indicates that it is highly desirable to identify simple measures to avoid the inadvertent creation of material in broadcast television that would be likely to induce photosensitive epilepsy and to identify measures to reduce the likelihood of the occurrence of such stimuli in broadcast television. The World Health Organization (WHO) has expressed interest to Study Group 6 in being kept informed of developments in this area.
Implanted and portable devices
EMF can cause RF interference to active implanted or portable medical devices. Insulin pumps and cardiac pacemakers belong to this class and, in the future, there may be an increasing number of these devices. Also the range and the number of different new devices appears to be increasing, e.g. portable monitors, prosthetic aids for sight and motion. Generally speaking, pacemakers and other medical devices could suffer interference from radiated EMF. However in the case of electromedical implanted devices, RF interference problems have not yet been completely solved due to the lack of full awareness of the problem by manufacturers and suppliers.