or circuit breaker. SAE document AS8003
Minimum Performance Standard for Automatic Pressure
Altitude Reporting Code Generating Equipment
states that “a means shall be incorporated in the
equipment to indicate the loss of electrical power or the effect thereof, unless the electrical power to
operate the code generating equipment is supplied by an ATC Transponder which also supplies an
indication of this power loss.” This is typically accomplished by using the switched A+ output from
the transponder or by connecting the SAE5-35 power input to the transponder circuit breaker. Alter-
natively, the two power pins, 8 and 14, are internally connected in the SAE5-35. Only one of these
connections is necessary to supply power to the unit. The unused connection can be used to drive a
panel-mounted indicator if desired.
All transponder functions including the Grey code output are on the 15 pin connector J4. The RS232
digital outputs for GPS and other avionics requiring this format as well as the AIM function are on
the 9 pin connector J5. The Grey code output on the transponder is disabled whenever Mode C on
the transponder is not selected.
Note: The RS232 serial data output is always present whenever
there is power to the SAE5-35 and the warm up time is com-
pleted, even when the Strobe/Enable line is not grounded.
Note: If power is supplied from the transponder, the RS232 and
AIM functions will be inoperative when the transponder is turned
off or removed from the aircraft.
Grounding the Strobe/Enable line on J4 pin 6 will enable the transponder Grey code data. There are
three methods used to do this.
1.
Permanently grounding this line.
2.
The transponder provides a switched ground enable signal.
3.
The transponder provides a strobe-ground enable signal.
The SAE5-35 is compatible with all three systems, refer to the appropriate transponder installation
manual for detail. Interconnect information for the most popular transponders can be found in Figure
3-6. For other makes of transponders, refer to the manufacturers installation manual.
Note: If the transponder being interfaced has a strobe output,
the AIM function will not operate properly and should not be
connected.
While several manufacturers use RS232 digital altitude data, their formats and baud rates may vary.
The SAE5-35 can accommodate most data formats by either grounding or leaving pin 4 on J5 open.
If pin 4 is left open, the output baud rate is 9600. If pin 4 is grounded, the output baud rate is 1200.
The RS232 interconnect information can be found in Figure 3-7.
Interconnect information for the most popular transponders can be found in Figures 3-6
.
The RS232
interconnect information can be found in Figure 3-7.
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