Crosstalk Levels of Speech Plus Data in Remote Communications Air-Ground (RCAG).

The Federal Aviation Administration FAA is proposing the addition of a digital data channel to the existing telephone lines which connect air route traffic control centers ARTCCs with remote communications air-ground RCAG sites to economically transfer Remote Monitoring System RMS parameters and control data between the ARTCCs and the sites. FAA Specification FAA-E-2699a establishes the maximum allowable interference level to pilotcontroller communications which would be allowed to result from the addition of the data channel. The tests described in this document were designed to verify that the requirements in FAA-E-2699a are sufficient to prevent disturbance to normal air traffic control ATC operations. The tests were performed by simulating and existing communications channel using data modems and samples of present-day Voice Frequency Control System VFCS equipment. Crosstalk levels of speech and data were measured under actual operating conditions. The test results indicated that the addition of an RMS data channel to existing FAA telephone lines is technically feasible and that the requirement in FAA-E-2699a concerning the data crosstalk in the audio portion of the communication channel is not adequate to prevent disturbance to normal ATC operations. The requirements concerning data crosstalk in the control portion and VFCS crosstalk in the data portion of the channel are sufficient. Author