Transponder

A transponder is a radio communication device that receives incoming signals and automatically answered and forwards. The term transponder is a portmanteau of the words transmitter and responder.

Passive transponders

Under passive transponders are systems, the energy required for communication and execution of internal processes relate exclusively from the write unit field. Passive transponders do not require their own power supply, but can only work over short distances.

The best-known type is the radio frequency identification RFID. Typical applications: identifying objects, Pet Registry chips or smart cards for an access control system. An active sensor reads (in conjunction with the computer) and decodes the data sent by the passive transponder.

Active transponders

Active systems have their own power supply. Either they have a built-in battery or be connected to an external power grid. This not only larger communication ranges are possible, even the management of large data storage or operation integrated sensor is realized. Simple active transponders are used for example in the identification of aircrafts: when the aircraft transponder receives a coded signal to a monitoring and control point and answered this signal at a predetermined frequency. This response signal is received from the monitoring point and displayed together with the radar echo.

In addition to the pure forms of passive or active systems exist semi-active transponder.

Communications satellites use transponders that reflect the received on the uplink frequency signal on a different frequency ( downlink ) frequency again.

Various transponder applications

ATC transponder

The ATC transponder (TPX or XPDR ) is a secondary radar transponder for identification of aircraft. This is done via the so-called transponder code, also called Squawk, a four-digit octal code that is set by the pilot on the transponder upon request by the air traffic control. Transponders have different operating modes:

• Mode A: Only the squawk is transmitted
• Mode C: Squawk and flight level ( altitude above normal pressure ) is transmitted
• Mode S: In addition to squawk and flight level a 24 -bit code is transmitted, which is uniquely assigned to each aircraft; In addition, the air traffic services unit specifically query certain transponder

Since 2008, may be flown in Germany in transponder airspace which requires only transponders, master the Mode S.

Although the transponder data are presented together with the primary radar data on the radar screens of air traffic control, is this is a stand-alone system. Most, however, the directional antenna for the transponder interrogation is fixedly mounted on the rotating primary radar antenna of the ground station. By a slight offset to the primary radar antenna the different signal delay times are corrected by the primary radar signal and the transponder signal so as to enable by a simultaneous presence of both signals, a better mapping of the primary echo to the secondary response.

Satellite transponder

Satellite transponder receive data in space and forward them, see Transponder (satellite).

Radar transponder

Radar Transponder reinforcing the echo of a radar signal, see Search and Rescue Radar Transponder ( SART ).

Anti-theft devices

The labels of an article surveillance system similar in function to most of a coil, the only tune a resonant circuit at a passage, or even of a complex passive RFID transponder which can be read interactively or automatically. The amount of information the retransfer of a transponder to the interrogator station varies depending on the type of 1 bit to complete product identification.

Digital locking systems

An anabolic to the secondary radar method locking system replaces mechanical lock cylinder. A small transponder in place of the conventional key unlocks doors and lockers at your fingertips. The system manages any number of locks and users and also offers special monitoring functions, such as time-dependent access and logging of presence. If a transponder key is lost, so this is simply blocked.

Remote control key in the car

Contactless key to the vehicle are part of modern vehicle equipment. They support the security of the vehicle to access stranger. Because of additional functional requirements such security solutions for securing the vehicle against use by strangers are usually limited to the boot process, an intervention in the driving process is not common. See also secondary radar and Keyless Go.

Railway transponder

Fixed active transponders in the safety systems of the railway are called beacons (French bake). These beacons describe a stationary safety technology in the ETCS concept and the ERTMS concept, technologically in the transition between the purely stationary track safety and the tensile travel safety.

Mobile active transponders are not yet used in the safety systems of the railway. Such solutions are only with the separation of infrastructure assurance ( Einfahrschutz ) and vehicle security ( train separation ) expected.

Card transponder

These passive transponder in credit card size (ISO 7810) are mostly used for personal identification. Areas of application are in access control systems, time attendance systems, but also for the billing of services and goods covers ( auto fuel, tolls, passenger transport, coffee machines, factory kitchens, ...). The advantages over the use of a magnetic stripe card are the easy handling, the resistance of the map to mechanical wear and the ability to store data on the card. The latter also enables the use as a prepaid medium, ie the card will be charged with credit and with each use of the card will be debited from this credit.

Animal transponder

For animal identification transponders are amplified by a special injector and an injection cannula implanted in the animal. The transponders are encapsulated in a Bioglashülle and adherent to the tissues of the animals. The marking is required by law in some European countries. Detailed description with animal registration.

Furthermore, the transponder of collars in milk production employed to allow for a power feed stations and also individual allocation, in order to monitor animal activity. The recognition of the animal in a herd management program and also in milking robots is also performed by the transponder.

Timing of sports events

In general, the transponder for automatic identification of persons are used. This is used in mass sporting events such as triathlons and marathons to identify the participants during the competition and record their times. One of the first systems is IPTAtime.

Warehousing

Transponders are used in automated warehouses, using the storage objects to be labeled with a RFID chip. Thereby can be automatically identified, the stored things.

Waste

Also in the waste are transponder eg used for detecting the emptied bins and assigning to the owner.