SELECTIVE IDENTITY SYSTEM

• US 3,719,943 A
• Filed: 02/18/1971
• Issued: 03/06/1973
• Est. Priority Date: 02/18/1971
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Alexander Rufus Applegarth
• Inventors: Applegarth, Alexander Rufus
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/116,523
• Time in Patent Office: 747 Days
• Field of Search: 343/6.5R,7.3
• US Class Current: 342/47
• CPC Class Codes: G01S 13/787 co-operating with direction defining beacons

Abstract

An improvement for aircraft DME equipment is disclosed, comprising electronic circuitry for selective identity of the DME station being tracked, and a method for providing such selective identity. The received identity signals are gated with an interrupt signal derived from the reply pulse detector, which interrupt signal carries information as to when the tracked ground station interrupts its replys to transmit its identity signals. Only those identity signals which coincide with interruption of reply signals are passed through the gate, such that other undesired identity signals are blocked, thereby avoiding ambiguity caused by simultaneous receipt of identity signals from other ground stations. The gated identity signal is connected to an audio device to produce a sound output. Alternatively, the interrupt signal may be connected directly to a separate audio signal generator, which generator produces audio signals corresponding to the identity signals of the tracked ground station.

Claims

1. In aircraft equipment which communicates with a ground based transponder station by transmitting signals to and receiving reply signals from such ground station, such ground station periodically interrupting transmission of reply signals to transmit identification signals, apparatus comprising:

a. a first path to detect said reply signals;

b. a second path to detect said identification signals;

c. interrupt detector means in said first path for detecting said interruptions of ground station transmission and for generating interrupt signals having time durations coincident with said interruptions;

d. gate means, receiving said interrupt signals from said interrupt detector means and said detected identification signals from said second path, for gating said identification signals only during the duration of said interruptions; and

e. indicator means driven by the output of said gate means for indicating said gated identification signals.

2. In aircraft equipment which communicates with a ground based transponder station by transmitting signals to and receiving reply signals from such ground station, such ground station periodically interrupting transmission of reply signals to transmit identification signals, apparatus comprising:

a. interrupt detector means for detecting said interruption of ground station transmission and for generating an interrupt signal having a time duration coincident with said interruption;

b. audio generator means, for generating an audio signal, being in a normally off condition, and generating said audio signal when driven by an input signal; and

c. coupling means, coupling the output of said interrupt detector means to the input of said audio generator, whereby said generated audio signal is coincident with said interruptions.

3. A process carried out in an aircraft for non-ambiguously identifying a ground station, which ground station receives signals from said aircraft and transmits reply signals to said aircraft, said ground station periodically interrupting such reply transmission and transmitting identification signals during such interruptions, comprising the following steps:

a. receiving and detecting said reply transmissions;

b. detecting said interruptions;

c. generating interrupt signals having time durations corresponding to said interruptions;

d. receiving and detecting said identification signals;

e. gating said identification signals with said interrupt signals, whereby identification signals are gated only when coincident with said interrupt signals; and

f. indicating said gated identification signals, thereby identifying said ground station to the exclusion of any other ground stations.