# US 4,399,425 A · Circuit for operating a flight navigation indicator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,399,425 A - Document ID: US4399425A - Status: Granted - Kind: A - Application number: 06/224,609 - Filed: 1981-01-12 - Granted: 1983-08-16 - Earliest claimed: 1981-01-12 - Assignees: Rockwell International Corporation - Inventors: Lothar J. Taylor - Web page: https://patentgrep.com/patent/US4399425A ## CPC - G01S 1/14: using amplitude comparison of signals transmitted simultaneously from antennas or antenna systems having differently oriented overlapping directivity-characteristics - G01S 1/047: {Displays or indicators (G01S1/06 takes precedence)} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A circuit for use in aircraft navigation equipment includes operational amplifiers to drive a cockpit indicator such as an electric meter linearly over a first predetermined range, constantly over a second predetermined range, and out of view over a third predetermined range. A first operational amplifier circuit provides a linear drive to the indicator and a second operational amplifier circuit controls the constant drive current to the meter and defines first and second breakpoints which begin the constant in view and constant out of view responses, respectively. The circuit needs only a single input signal for operation. ## Claims ### Claim 1 In an aircraft navigation system wherein course indicating information is displayed on a cockpit indicator, the improvement comprising: means for controlling said cockpit indicator for providing (1) a linear display on said indicator solely in response to a signal representing course information falling within a first signal range, (2) a first constant display on said indicator solely in response to said signal falling within a second signal range, and (3) an off-scale display on said indicator solely in response to said signal falling within a third signal range. ### Claim 2 (depends on 1) The system of claim 1 wherein said course information is provided by a signal a, where a is the signal from said first signal range for values of a less than a1; a is the signal from said second signal range for values of a which are greater than a1 and less than a2; and a is the signal from said third signal range for values of a greater than a2; wherein a1 and a2 are predetermined magnitudes of the signal a. ### Claim 3 In an aircraft navigation system which displays course information on an electric meter, the improvement comprising: an input providing a single signal representing course information; and means responsive solely to said signal for providing (1) a linear meter driving signal for input signal magnitudes less than a first predetermined magnitude, (2) a first substantially constant meter driving signal for input signal magnitudes greater than said first predetermined magnitude and less than a second predetermined magnitude, and (3) an off-scale meter driving signal for input signal magnitudes greater than said second predetermined magnitude. ### Claim 4 (depends on 3) The improvement of claim 3 wherein said single input is a current signal representing glide slope deviation. ### Claim 5 (depends on 3) The improvement of claim 3 wherein said single input is a localizer signal. ### Claim 6 (depends on 3) The improvement of claim 3 wherein said single input is a current signal wherein said first predetermined magnitude is approximately equal to 0.150 mA and said second predetermined magnitude is approximately equal to 1.0 mA. ### Claim 7 An apparatus for displaying course information in an aircraft comprising: an electric meter; a first operational amplifier having at least one input for receiving a navigation signal to be displayed on said meter and having an output voltage for providing a linear meter driving signal to said meter solely in response to said navigation signal; a second operational amplifier having inputs coupled to compare the output of said first operational amplifier and a predetermined voltage, and having an output coupled to provide a first substantially constant meter driving signal to said meter when the output voltage of said first operational amplifier is less than said predetermined voltage; and semiconductor means for controlling the output of said second operational amplifier to cause an off-scale meter driving signal to be provided to said meter to produce an off-scale meter indication when the output of said second operational amplifier reaches a predetermined value. ### Claim 8 (depends on 7) The improvement of claim 7 wherein said predetermined voltage which is compared with the output of said first operational amplifier is established to produce an output of said second operational amplifier when the navigation signal is a glide slope signal and exceeds two dots. ### Claim 9 (depends on 7) The improvement of claim 7 wherein said navigation signal is a glideslope signal. ### Claim 10 (depends on 7) The improvement of claim 7 wherein said navigation signal is a localizer signal. ### Claim 11 (depends on 7) The improvement of claim 7 wherein said semiconductor means is a Zener diode. ### Claim 12 An aircraft navigation display system comprising: means for receiving a single input signal representing course information; means for providing a display representing said course information; and means responsive solely to said single input signal for causing (1) a linearly changing display representing said course information during a first display range, (2) a first constant display representing said course information during a second display range, and (3) a second substantially constant display representing said course information during a third display range. ### Claim 13 In an aircraft navigation system wherein course indicating information is displayed on a cockpit indicator, the improvement comprising: means for controlling said cockpit indicator for providing (1) a linear display on said indicator solely in response to a signal representing course information falling within a first signal range, (2) a first constant display on said indicator solely in response to said signal falling within a second signal range, and (3) an off-scale display on said indicator solely in response to said signal falling within a third signal range, said second signal range falling between said first and third signal range. ### Claim 14 An aircraft navigation display system comprising: means for receiving a single input signal representing course information; means for providing a display representing said course information; and means responsive solely to said single input signal for causing (1) a linearly changing display representing said course information during a first display range, (2) a first constant display representing said course information during a second display range, and (3) a second substantially constant display representing said course information during a third display range, said second display range falling between said first and third display range. ### Claim 15 An apparatus for displaying course information in an aircraft comprising: an electric meter having a first and second input; a first operational amplifier having an inverting and a non-inverting input and an output, said inverting and non-inverting inputs being coupled to receive a navigation signal to be displayed on said meter, said inverting input also being coupled to the first input of said meter and the output of said first operational amplifier being coupled to the second input of said meter; a second operational amplifier having an inverting input and a non-inverting input and an output, said inverting input of said second operational amplifier being coupled to a variable reference voltage, said non-inverting input being coupled through an impedance to the output of said first operational amplifier; a zener diode having an anode and cathode with said anode coupled to the output of said second operational amplifier; and a diode rectifier having an anode and cathode, the cathode of said diode rectifier being coupled to the cathode of said zener diode and the anode of said diode rectifier being coupled to the first input of said meter and also through an impedance to the inverting input of said second operational amplifier; the cooperation of said first and second operational amplifier with said zener and diode rectifiers being such as to provide a linear meter driving signal to said meter solely in response to said navigation signal during a first display range, to provide a first substantially constant meter driving signal solely in response to said navigation signal during a second display range, and to provide a third substantially constant meter driving signal to said meter to produce an off-scale meter indication during a third display range, said second display range being located between said first and third display range.