 giving the radio a cross-reference to other stations when travel information is being transmitted. Music/Speech - A data flag that allows for the relative levels of speech and music to be altered. Programme identification - This is a station code used in conjunction with the alternative frequency signal to locate suitable alternative transmitters for a given programme. Each service is allocated its own unique identifier. Programme identification number - This signal identifies a given programme, and allows for a radio or recorder to be turned on when the identification number is recognized. Programme type selection - This signal identifies one of 15 types of programme, allowing selection of the type of listening rather than by station. Programme service name - A signal that carries the station name and allows this to be displayed by the receiver. Radio text - This allows information about the programme to be displayed by the radio. Transparent data channel - This allows data to be downloaded over the radio. TP/TA Travel service - These signals enable the travel information to be heard, regardless of the choice of listening. Digital radio (digital audio broadcasting - DAB) Most current broadcast techniques use analogue techniques to carry the audio on the carrier. However, with the move to the use of digital techniques because of the improved performance a digital system is now available in a number of countries. Called digital audio broadcasting 216 Newnes Guide to Radio and Communications Technology (DAB) it gives many improvements and new features over the existing AM and FM systems in use. DAB gives major improvements over FM, particularly for those in automobiles. FM suffers particularly when signal strengths are low and the signal is being received by a number of different paths. Reflections off buildings, hills and other objects cause distortion of the signal, and in addition to this the tuning has to be altered when passing from the coverage area of one transmitter to the next. With the increase in the nu