Device for calling a ground station by an aircraft

A ground station system for automatically monitoring radio communication calls from aircraft which transmit and receive traffic over one of a predetermined number of high frequency carriers, comprising:

• I. in said aircraft:
• A. means for transmitting from said aircraft a calling code signal of tone frequencies of given spacing and duration indicating in its code;
• 1. a ground station to be called,
• 2. the direction sector of said aircraft with respect to said ground station,
• 3. the modulation scheme, and
• 4. the party being called at said ground station;
• and
• Ii. at said ground station:
• A. separate receivers for each of said high frequency carriers,
• B. decoding means connected to all of said receivers for detecting a complete and correctly received calling code signal from said aircraft over any one of said carriers,
• C. a transmitter for transmitting traffic from said ground station to said aircraft, and
• D. means for selecting a transmitter for said one carrier frequency and switching the transmitter antenna towards the direction of said aircraft.

A ground station method for automatically monitoring radio communication calls from aircraft which transmit and receive traffic over one of a predetermined number of high frequency carriers, comprising the steps of:

• I. in said aircraft:
• A. generating a calling code signal comprising:
• 1. a ground station calling part of a repeated spaced pair of predetermined tone frequencies, each of the same duration,
• 2. an information part of a repeated spaced quadruplet of predetermined tone frequencies, each of the same and another given duration, indicating:
• a. the direction sector of said aircraft with respect to the called ground station,
• b. the modulation scheme, and
• c. the party being called,
• B. modulating and transmitting said code signal on one of said high frequency carriers, and
• C. transmitting and receiving traffic from said called ground station on said one carrier after calling code signal has been correctly received by said party;
• and
• Ii. at said ground station:
• A. separately monitoring each of said high frequency carriers for amplitude and single side band reception, omni-directionally or directionally,
• B. detecting the tone frequencies of said calling code signal on any one of said carriers,
• C. determining the duration and spacing of said tones in said calling code signal for indicating the complete and correct reception of said calling code signal,
• D. responding to the correctly received calling part of said calling code signal for said selected ground station,
• E. decoding said information part of said calling code signal for determining:
• 1. the direction sector of said aircraft from said selected ground station,
• 2. the modulation scheme, and
• 3. the party being called,
• F. selecting the ground station traffic transmitter for the carrier of said code signal,
• G. switching the traffic transmitting and receiving ground station antennas towards the direction of said aircraft in response to said determined direction from one part of said information part of said code signal,
• H. setting said ground station traffic transmitter and receiver to operate according to said scheme determined from another part of said information part of said code signal, and
• I. connecting said ground station traffic transmitter and receiver to the called party determined by a third part of said information part of said code signal.