Narco Avionics AR850 Installation And Operation Manual - page 21
INSTALLATION
SECTION 2
7/03
2-9
2.4 ELECTRICAL INSTALLATION
This section presents the required technical information necessary to plan
and execute electrical installation of the AR850. Refer to Section 2.4.7
"Interconnect Wiring Diagrams" for installation of the AR850 to Narco and
King transponders.
2.4.1 AR850 To Transponder Compatibility
The AR850 is compatible with all Narco TSO'd transponders as noted here:
1.
AT155/AT150 : Directly compatible.
No modifications required.
2.
AT50/50A : Directly compatible when Narco Service Bulletin AT-50A-
5 dated Feb. 19, 1975 is performed on the transponder.
2.4.2 AR850 ENABLE Requirements
Normally the transponder controls the enabling of the altitude reporter when
in the altitude mode (Mode C). When the transponder is operating in its
normal IDENT mode (Mode A), the altitude reporter is inhibited. Transponders
may supply an ENABLE and/or STROBE output; those which supply only a STROBE
output will not enable the AR850. The requirements are listed below.
1.
Activating the AR850 requires that a ground be applied to P101-6,
the ENABLE input, only when the transponder is placed in the
altitude mode. Normally the transponder would be the ground
source. The installing agency should investigate the transponder
ENABLE source and determine if the source is wired permanently to
ground, switched to hard ground in the altitude mode, or grounded
through an active device (transistor or IC) when in the altitude
mode. If the ground source is an active device, when it is ON
(active low), it must pull the transponder ENABLE output down to
within 0.2V of ground or less. The diode in series with the AR850
ENABLE line has a junction voltage of 0.5V. This voltage must be
added to the transponder's active device junction voltage, and the
sum not to exceed 0.8V or else the EPROM and the 12 bit A/D
Converter in the AR850 cannot be enabled.