Answer device for an interrogation-answer system having time dependent differing codes and provision of special signal means

Claim 2

A transponder of a secondary radar interrogation answer system comprising: means for receiving a programmed sequence of interrogation codes from an interrogation device, code means in said transponder for internally producing the programmed sequence of interrogation codes and a corresponding related programmed sequence of answer codes, said internally produced interrogation and answer codes each including past, present and future codes representing past, present and future time, means for comparing the internally produced interrogation codes with a received interrogation code, means responsive to a coincidence between the received code and one of the internally produced interrogation codes, means for transmitting back to the interrogation station an answer code corresponding to the coincidence effected with one of said internally produced interrogation codes, first storage means for storing an answer code corresponding to a future interrogation code and means for transmitting a future answer code to an interrogation device in place of an answer code normally effected in response to coincidence, as a special situation signal representing an emergency situation.

Claim 3

A transponder according to claim 1, comprising clock means connected to said code means and operable to produce clock pulses at a frequency that is synchronized with the interrogation device so that said code means produces the internally generated codes in synchromism with codes which are to be received from the interrogation device, further storage means connected to said code means and including a plurality of first storage sections for storing respective past, present and future internally generated interrogation codes, said code means being connected to said first storage means, which include a plurality of second storage sections for stOring respective past, present and future internally generated answer codes, said means for comparing including a plurality of coincidence circuits connected for receiving an interrogation code and to respective ones of said first storage sections and individually operable in response to coincidence between a received interrogation code and one of the stored interrogation codes to indicate synchronism, lead or lag between the two coincident codes, an answer output, a plurality of gating means interposed between respective ones of said second answer code storage sections and said answer output and connected to and controlled by respective ones of said coincidence circuits to gate an answer code to said answer output, additional gating means connected between an answer code storage section and said answer output, and said means for transmitting a future answer code including means for triggering said additional gating means to place a future answer code on said answer output.

Claim 4

In a transponder according to claim 2, wherein said means for triggering includes a manually controlled switch.

Claim 5

In a transponder according to claim 2, wherein said means for triggering includes impact responsive switch means.

Claim 6

In a transponder according to claim 2, wherein said storage device which stores said future answer code is connected in series with said second storage devices to receive and store as said special situation signal one of said answer codes which corresponds to a code representing an extreme future time.

Claim 7

In a transponder according to claim 5, wherein said additional gating means includes an AND gate, and said trigger means is connected to an input of said AND gate, other trigger means including an OR gate and connections from each of said coincidence circuits to inputs of said OR gate, said OR gate connected to said AND gate, inverter means connected between the first-mentioned trigger means and said plurality of gating means to inhibit gating of an answer code from said second storage sections upon gating of the code from the storage section which stores said future answer code.

Claim 8

In a transponder according to claim 5, wherein said additional gating means includes an AND gate, said trigger means is connected to an input of said AND gate, said answer storage sectin section storing said future answer code connected to and input of said AND gate and one of said coincidence circuits connected to an input of said AND gate to gate said special signal upon coincidence of a corresponding interrogation code and the conjunct operation of said trigger means.

Claim 9

In a transponder according to claim 1, wherein said means for storing said answer code which corresponds to a future interrogation code is included in means for storing answer codes corresponding to past, present and future interrogation codes, and comprising means for operating said transmitting means to emit said special signal answer code.

Claim 10

In a transponder set forth in claim 8, wherein said means for storing answer codes corresponding to past, present and future interrogation codes comprises a shift register which constitutes the respective storage sections.

Claim 11

In a transponder according to claim 8, comprising means for preventing transmission of an answer code corresponding to a present interrogation code in response to operation of said means for operating said transmitting means.