Secure I/P
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorLaddie T. Rhodes
Life of this patent
Estimating the term…
Abstract
An improvement in the present radar/IFF equipment used by the military whereby the transponding equipment, when used in crypto-secure Mode 4, is enabled to reply with its unique coded identification number (Mode 2 reply) after it has made its Mode 4 reply. This is accomplished by adding an AND gate and a delay means to the present equipment. The AND gate is connected to couple the Mode 4 three-pulse interrogation to the delay means if it is received at the same time the I/P activate switch is in its operating position. The delayed three-pulse interrogation signal is coupled to the encoder and activates a Mode 2 reply. The ground equipment is also modified to enable it to faithfully reproduce the entire video output of its interrogator section.
Claims2
In combination with the transponder of an AIMS which includes a decoder having at least Mode 2 and Mode 4 output terminals, an encoder having at least a Mode 2 input terminal, an I/P-activate switch, one side of which is grounded, the other side being connected to said encoder, a mode switch connected between the Mode 2 output terminal of said decoder and the Mode 2 input terminal of said encoder, a Mode 4 computer having a Mode 4-reply output terminal and receiving as an input the signal on the Mode 4 output terminal of said decoder, apparatus comprising:
- gating means coupled to the ungrounded side of said I/P-activate switch and to receive the Mode 4 signal from said decoder, said gating means being normally in a switch-open condition but being placed in a switch-closed condition by receipt of a Mode 4 reply signal from said computer when said I/P-activate switch is closed;
- and
- delay means, coupled to receive the output of said gating means, for delaying its input signal by a predetermined amount of time, the output of said delay means being coupled to the Mode 2 input terminal of said encoder to active the encoder to generate a Mode 2 reply signal, whereby a Mode 2 identification signal is transmitted after every Mode 4 reply.
In an AIMS-Mark XII-type aircraft IFF transponder including a decoder having at least Mode 2 and Mode 4 output terminals, an encoder have at least a Mode 2 input terminal, an I/P-activate switch, one side of which is grounded, the other side being connected to said encoder, a mode switch connected between the Mode 2 output terminal of said decoder, and the Mode 2 input terminal of said encoder, a Mode 4 computer having a Mode 4-reply output terminal and receiving as an input the signal on the Mode 4 output terminal of said decoder, means comprising:
- gating means coupled to the ungrounded side of the I/P-activate switch and to the Mode 4-reply output terminal of said computer, said gating means being normally in a switch-open condition but being placed in a switch-closed condition by the simultaneous closure of the I/P-activate switch and receipt of a Mode-4-reply signal from said computer;
- and
- delay means, coupled to receive the output of said gating means, for delaying its input signal by a predetermined amount, the output of said delay means being coupled to the Mode 2 input terminal of the encoder of said transponder to activate the encoder to generate a Mode 2 reply signal, whereby a Mode 2 identification signal is transmitted after every Mode 4 reply.
Dependencies are inferred from the claim text.