Narco Avionics AR850 Installation And Operation Manual - page 22
NARCO AVIONICS AR850
2-10
7/03
2.
If the transponder's internal ENABLE source is a permanent ground
and not altitude mode controlled, the AR850 will be permanently
enabled. When the altitude reporter is permanently enabled, the
companion transponder must have additional internal circuitry
designed to inhibit the transmission of altitude information when
it is operating in other than the altitude mode. If the
transponder cannot meet this requirement, the AR850 ENABLE input
must be controlled by a panel mounted switch.
2.4.3 Primary Power Requirement
a)
The AR850 accepts 11 to 32 Vdc for its primary power; therefore NO
voltage converter is required for 28V aircraft electrical systems.
b)
The AR850 incorporates an "altitude sensor" heater which is
energized when power is applied. Initial current draw is 1.4 amps
for approximately 3 minutes, the time required to heat the sensor,
after which the current drops to 0.35 amps average. The heater
current is only required for warmup.
c)
Primary power is applied to the rear connector, J101, between pins
14 and 15 from the avionics bus. Do not use switched A+ output
from the transponder. Connect a 2 amp resettable circuit breaker
between the AR850 and the avionics bus. Pins 8, 14 are connected
together internally.
d)
J101 pin 15 is airframe ground. Pins 1, 7, 15 are connected
together internally.
2.4.4 AR850 Altitude Code Line Characteristics
The AR850 altitude code line drivers comprise a high voltage, high sinking
current, Darlington transistor array (Sprague ULN2003A). All drivers feature
open collector outputs as shown below.
In the "OFF" state, the collector can accept from the transponder any pull
up voltage up to 50 Vdc.
In the "ON" state, the collector to emitter saturation is 0.75V at 50 ma. or
1.1V at 100 ma. sinking currents.