Annotations Telemedicine in paediatric cardiology

The technology The explosion in the number of telemedicine projects is largely due to major advances in telecommunications technology, which have made it possible to transfer large amounts of data quickly. One of the most significant developments is the introduction of integrated services digital network (ISDN) lines to the telephone network of most western countries. These lines have the capacity to allow rapid transfer of the large amount of information necessary to transmit moving images such as ultrasound pictures. Before transmission the image is converted to a digital signal by a “codec”, which is usually a desktop videoconferencing unit. Transmission is then possible using ISDN, fibreoptic, radiowave or even satellite networks. After transmission a second codec at the receiving end reverses the process reconstructing the image. The information carrying capacity of any telecommunication system is measured in terms of bandwidth, the unit of which is bits/ second. The technological sophistication of systems ranges from the standard analogue telephone line (38 kbits/ second) to national broadband networks such as the British universities superJANET system with a bandwidth of 600 Mbits/second. Two ISDN lines have a bandwidth of 128 Kbits/second.