Version 16.10 AF-6600 AF-5000 Series Install Manual 103
Ident Switch Input (optional)
AF-5000 has an IDENT button in its transponder menu that is normally used to ident when requested by ATC.
However, the ident switch input allows the IDENT function to be selected using a remote switch. The input is active
low, and will be asserted when the voltage to ground is pulled below approximately 4 Volts. Therefore, a momentary
switch to ground should be installed on this output if a remote ident switch is desired.
Squat Switch Input (optional)
The Squat switch input allows the transponder to automatically switch between Airborne and Ground modes, and
affects both the Mode S reply behavior and the ADS-B reporting behavior. The input will be asserted when the voltage
to ground is pulled below approximately 4 Volts. The logical sense of the input can be programmed to be either active
low or active high in the AF-5000 Setup Menu.
This must be a mechanical switch that accurately reflects the aircraft’s on-ground status. Mode-S certification
requirements state that this cannot be a simple airspeed switch.
On an aircraft with no appropriate squat switch circuit this input should be left unconnected, and the transponder
programmed to either ignore the input or use its “automatic” airborne/ground capability. See the AUTO ALT/GND
SWITCH setting in the Transponder Settings section of this chapter for further information about this capability.
External Standby Input (optional)
This input, when held low, places the transponder in Standby mode. It should be used to switch between transponders
in an installation with two transponders. The input is active low, and will be asserted when the voltage to ground is
pulled below approximately 4 Volts.
Direct Serial GPS Position Input
Although the AF-5000 can send its GPS information to the SV- 261 for use with its ADS-B position-reporting capability,
The AF-5000 GPS does not meet any certification standard, and is not TSO’d. Additionally, appropriately certified GPS
units that can provide position for regulatory-compliant ADS-B installations may need to be connected directly to the
ADS-B Out device (in this case, the SV- 261) for compliance credit. For these purposes, a dedicated direct serial input is
provided on the SV- 261 module that allows an appropriate GPS receiver serial output to be connected directly to the
SV- 261.
If you connect a GPS to this direct input, you must install a 1.21k resistor (included with the SV -261) between the GPS
and the SV-261 as shown.
The SV- 261 GPS input can recognize the following protocols:
• Industry standard “Aviation” protocol
• Freeflight GPS proprietary protocol
• Garmin proprietary ADS-B protocol (compatibility not verified)
Some of the protocols listed above may not contain all the required data for a compliant ADS-B message, depending
on the intended airspace regulations. Further information can be found in the GPS Data section under the
Transponder Settings of this chapter.
(US-Only) Direct Serial GPS Position Input for FAA 2020 ADS-B Out Mandate Compliance
To comply with the 2020 ADS-B Out Mandate in the US, the GPS position used for ADS-B Out position reports must be
directly connected to a suitable ADS-B Out device (in this case, the SV- 261), and, that GPS must meet TSO C166b. DO
NOT connect any GPS (including AF-5000 own GPS outputs) that does not meet TSO C166b directly to the
transponder.
It is important to note that in the US, the ADS-B Out “mandate” and its associated GPS requirements do not go into
effect until 2020. If you do not already have an appropriately TSO’d WAAS IFR GPS in the aircraft, you may continue to
leave this Direct Serial unconnected for the time being. Instead the AF-5000 has the capability to send its GPS position
to the SV- 261 . Although The AF-5000’s GPS output does not meet the 2020 requirements, it can be used until then
to “wake up” the ADS-B ground stations so that they report back traffic targets around your aircraft’s position.
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