Transponder

If the vehicle is equipped with an ADS-B Transponder or will be at some point, it is possible to configure and transmit ADS-B messages using UgCS. As of this moment, UgCS supports Sagetech XPS-TR Mode S transponders. The following main functions for ADS-B Transponder configuration and usage are available:
• To set ADS-B modes;
• To set parameters;
• To display annunciators;

The following list of parameters are available:
• SQUAWK: must contain of four octal digits. Allowed digits are: 0, 1, 2, 3, 4, 5, 6, 7.
• ICAO Address: must contain of six hexadecimal digits. Allowed symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F.
• Aircraft registration (tail number): must contain of up to 8 symbols. Allowed are: 0-9, A-Z.
• Flight ID: must contain of up to 8 symbols. Allowed are: 0-9, A-Z.
• IDENT* flag: Yes (single direction button)
• External altitude: Yes/No

http://aviation.stackexchange.com/questions/3049/how-does-ident-work

Transponder parameter usage:
• ICAO Address and Aircraft Registration/Tail number will remain the same for a specific vehicle in most cases. These parameters can be set in the Vehicle Parameters.

• SQUAWK parameter can be defined when necessary at any time during the flight (ADS-B settings menu for reference, A).

• Flight ID should be set during preparation for take-off. That is done in the Preflight section (ADS-B settings menu for reference, B).

Available transponder modes (ADS-B settings menu for reference, C):
• OFF – Transponder is turned OFF
• STBY – Standby mode. Transmission does not happen, the device is set to low power consumption, and is ready for a start-up with reduced warm-up time.
• ON – Transponder is transmitting and receiving data, but no altitude information is transmitted.
• ALT – Same as “ON” mode with the additional transmission of vehicle altitude.

The following error codes can be displayed:

• XPDR – General error code that is displayed if any of the following errors have occurred.
• TEMP – If the transponder temperature sensor reports an error.
• GPS – Displayed if there is no GPS signal.
• ICAO – If there is no valid ICAO address set.
• ES – Displayed if the extended squitter has failed.