Installation guide

SV-XPNDR-261/262 Installation, Configuration, and Testing
11-10 SkyView System Installation Guide - Revision R
Ident Switch Input (optional)
SkyView 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
SkyView Setup Menu.
If connected, 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.
Alternatively, 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 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 SkyView can send its GPS information to the SV-XPNDR-261/262 for use with its ADS-
B position-reporting capability, SkyView’s 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-XPNDR-261/262) for compliance credit. For these purposes, a
dedicated direct serial input is provided on the SV-XPNDR-261/262 module that allows an
appropriate GPS receiver serial output to be connected directly to the SV-XPNDR-261/262.
If you connect a GPS to this direct input, you must install a 1.21k resistor (included with the SV-
XPNDR-261/262) between the GPS and the SV-XPNDR-261/262 as shown in Figure 76.
The SV-XPNDR-261/262 GPS input can recognise the following protocols:
 Industry standard “Aviation” protocol
 Freeflight GPS proprietary protocol
 Garmin proprietary ADS-B protocol