B737 Transponder (ATC/TCAS) Panel

Transponder (ATC) Selector

• 1 – Selects transponder No. 1.
• 2 – Selects transponder No. 2.

Air Traffic Control (ATC) Code Selector

• Rotate – Sets transponder code in the transponder.

Air Traffic Control (ATC) Code Indicator

• Displays transponder code.
• Shows the operating transponder (1 or 2).

Transponder Mode Selector

• TEST – Starts ATC transponder functional test.
• STBY (standby) – Does not transmit.
• ALT (altitude reporting) OFF – Transponder operates without altitude reporting.
• ALT (altitude reporting) ON – Transponder operates with altitude reporting.
• TA (traffic advisory) – Enables the display of traffic advisory (TA) targets.
• TA/RA (resolution advisory) – Enables the display of traffic advisory (TA) and resolution advisory (RA) targets.

Identification (IDENT) Switch

• Push – Transmits an identification signal.

Transponder (ATC) FAIL Light

• Illuminated (amber) –
  • Indicates transponder malfunction, or
  • ADS-B inoperative.

Altitude (ALT) Selector

• 1 – Enables altitude reporting from air data computer No. 1.
• 2 – Enables altitude reporting from air data computer No. 2.