User Guide

Series III Avionics
Pilot's Guide
Page 21
SBY - Applies power to the TRS-42A system
circuits without activating the transmitter.
The last displayed code appears in the
upper line of the display and may be
changed with CODE SELECT knobs.
Lower line of the display is blank.
ON - Enables the TRS-42A to respond to ATC
radar interrogations. Altitude is not
encoded into the TRS-42A response.
ALT - Same as ON except altitude is encoded
into the response when the TRS-42A is
interrogated by ATC radar. Altitude is not
displayed.
VFR - Automatically selects and displays 1200
as the transponder code (other codes
may be programmed for non-U.S.A.
operation). Altitude is still encoded into
responses in this mode, but is not
displayed.