The Application of Altitude Telemetering to the ICAO Secondary Surveillance Radar System

The operational requirements for telemetering altitude are listed, together with general aspects of the system which can affect implementation. The special problems which arise in the application of altitude information to the ICAO SSR system are discussed, and it is shown that it is essential to incorporate certain design features in the communications channel and in the coding system to minimize garbling. The experimental United Kingdom system of altitude telemetering is briefly described, together with proposals for expanding the encoding scale to cover any future requirement.