Cessna 152 1978 - Page 182

CESSNA AIRCRAFT COMPANY FOR TRAINING USE ONLY
MODEL 152 9-42
Figure 1. Cessna 400 Transponder and Altitude Encoder (Blind)
1. FUNCTION SWITCH – Controls application of power and selects transponder operating mode as
follows:
OFF – Turns set off.
SBY – Turns set on for equipment warm-up or standby power.
ON – Turns set on and enables transponder to transmit Mode A (aircraft identification) reply
pulses.
ALT – Turns set on and enables transponder to transmit either Mode A (aircraft
identification) reply pulses or Mode C (altitude reporting) pulses selected automatically by
the interrogating signal.
2. REPLY LAMP – Lamp flashes to indicate transmission of reply pulses; glows steadily to indicate
transmission of IDENT pulse or satisfactory self-test operation. (Reply lamp will also glow
steadily during initial warm-up period.)
3. IDENT (ID) SWITCH – When depressed, selects special pulse identifier to be transmitted with
transponder reply to effect immediate identification of aircraft on ground controller’s display.
(Reply lamp will glow steadily during duration of IDENT pulse transmission.)
4. DIMMER (DIM) CONTROL – Allows pilot to control brilliance of reply lamp.
5. SELF-TEST (TST) SWITCH – When depressed, causes transponder to generate a self-interrogating
signal to provide a check of transponder operation. (Reply lamp will glow steadily to verify self-
test operation.)
6. REPLY-CODE SELECTOR SWITCHES (4) – Select assigned Mode A reply code.
7. REPLY-CODE INDICATORS (4) – Display selected Mode A reply code.
8. REMOTE-MOUNTED DIGITIZER – Provides an altitude reporting code range of -1000 feet up to
the airplane’s maximum service ceiling.