Transponder Operating Controls and Indicators -- Continued
Up - Increments information on eight-character display. When held in up position, continuously
increments displayed information. When momentarily held in up position, provides single
Middle - Disables update of display information. Normal switch position.
Down - Decrements information on eight-character display. When held in down position,
continuously decrements displayed information. When momentarily held in down position,
provides single decrement.
M-1, M-2, M-3/A, M-C TEST/ON/OUT three-position switches.
TEST - Enables transponder to perform self-test in selected mode. During TEST, the selected
mode is radiated. If self-test is initiated with MASTER switch in STBY, FAIL message will be
displayed. Momentary switch position.
ON - Enables respective mode. Normal switch position.
OUT - Disables respective mode. Transponder will not reply to interrogations in the disabled
When M-3/A switch is set to OUT, Mode C and Mode S are disabled and self-test
(BIT) for Mode C is disabled. If Mode S is enabled and M-3/A switch is set to TEST,
Mode 3/A and Mode S functions of the transponder and the TCAS processor are
tested. If the TCAS processor is on and M-3/A switch is set to TEST, a TCAS FAIL
message will be reported. If Mode S is disabled and M-3/A switch is set to TEST,
Mode 3/A functions of the transponder will be tested, and then the display will in-
dicate MODE S DISABLE.
RAD TEST spring loaded two-position switch.
RAD TEST - When held in up (RAD TEST) position enables the transponder to reply to Mode
4 interrogations with a "Verify Bit 1" set. When momentarily pressed to up position, overrides
the on-the-ground reply inhibit to Mode 3/A, Mode C, ATCRBS/Mode S All-Call, and Mode S
only All-Call interrogations. Each time the RAD TEST switch is momentarily pressed up, the
transponder will override the on-the-ground reply inhibit for 1 minute (up to 5 minutes total).
OUT - Enables normal transponder operation. Normal switch position.
MODE 4 CODE ZERO/B/A/HOLD PULL TO ZERO four-position rotary switch.
ZERO - Clears Mode 4 code held in Crypto Appliqué or external Mode 4 Computer. Pull to
rotate to (protected) position.
B - Selects next code period.
A - Selects current code period.
HOLD - Activates Mode 4 code hold logic in Crypto Appliqué or external Mode 4 Computer,
which prevents the loss of Mode 4 key if power is removed and landing gear has cycled (up
and down). If HOLD is activated, Mode 4 key may only be zeroized by manually selecting
ZEROIZE on Crypto Appliqué or external Mode 4 Computer, or by selecting ZERO on this
switch. Momentary switch position.
MODE 4 TEST/ON/OUT three-position switch.
TEST - Enables transponder to perform Mode 4 self-test. During TEST, Mode 4 code is not
radiated. Momentary switch position.
ON - Enables Crypto Appliqué or external Mode 4 Computer to reply to compatible Mode 4
interrogations. Normal switch position.
OUT - Disables Mode 4 operations. When Mode 4 interrogations are received, transponder
will not reply and a Mode 4 Caution will be sent to platform warning panel, (provided Crypto
Appliqué or external Mode 4 Computer is installed).
MODE 4 AUDIO/LIGHT/OUT three-position switch.1