User Guide
Series III Avionics
Pilot's Guide
Page 20
TRS-42A Controls
Function Selector
OFF - Deactivates the TRS-42A System.
Records the last data displayed into the
system's non-volatile memory.
TST - Displays barometric altitude from an
encoding altimeter in the lower line of the
display. An unsuccessful test displays
FAIL in upper line of the display.
Pressing the IDENT button in the TST
mode causes upper line of the display to
read 8888 and lower line to read 88888.