Narco AT-150 Transponder
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2.5 Electrical Installation
2.5.1 Power And Interconnect Cable
The Installation Kit provides an 18 pin Molex connector along with sufficient pins for fabrication of the power and interconnect cable. Figure 2-4 presents the electrical connections and Figure 2-5 presents a system orientation diagram.
All signal leads should be 22 AWG. A+ and ground leads should be 16 AWG. The ground lead should be connected directly to airframe ground.
A 1.5 amp circuit breaker should be provided between the unit and the aircraft power bus.
Figure 2-4 - Power and Interconnect Cable
Figure 2-5 - Orientation Diagram
2.5.2 Cable Fabrication
Figure 2-6 - Crimping Tool
Crimping with Pliers
The lead pin Terminal connection using the Molex hand crimper provides a superior connection than with pliers. However, with care, a satisfactory connection can be made without the crimper.
2.5.3 28 Vdc Operation
The AT 150 has been designed for 14V operation. Installation in aircraft with 28V electrical systems win require the addition of the external voltage converter, Model MP 10. Refer to Systems paragraph 1.10 for installation details.
Commencing with AT 150 Chassis Level Code JB do not change the pilot lamp jumpers!
These units contain an external 14/28 vdc switch for this purpose. The switch, for proper lamp brilliance, should be set to agree with that of the aircraft's bus voltage.
Figure 2-7 - Pilot Lamp Conversion (Switch)
Pilot Lamp 14/28v Jumpers ( Units without external switch.)
The AT 150 pilot lamps are factory wired for 14v operation. Installation in aircraft with 28v electrical systems will require that the lamp circuitry be wired in series. To connect the lamp circuit for 28v operation, refer to Figure 2-8 and proceed as follows:
Figure 2-8 - Pilot Lamp Conversion (Jumpers)
2.5.5 External Suppression
The AT 150 transponder may be externally suppressed by other avionics equipment whose transmissions may be interfered with by simultaneous AT 150 transmissions. P101-15 may be connected to equipment that supply positive suppression pulses. P101-1 may be connected to equipment that supply negative suppression pulses.
In aircraft equipped with dual transponders, P1O1-1 of both transponders may be connected to a remote SPDT switch which will alternately suppress the transponders by placing the appropriate P101-1 at ground potential. This switch may be located at any convenient place in the cockpit and labeled appropriately.
2.5.6 Remote IDENT
P1O1-17 provides for the connection of remote IDENT switch. This switch should be a momentary SPST type and connected such that activation places P1O1-17 at ground potential. This switch may be located at any convenient place in the cockpit and labeled appropriately.
2.5.7 Altitude Digitizer
P101 pins 5 through 14 provide for the connection of an altitude digitizer. The altitude digitizer, sensing atmospheric pressure, converts pressure/altitude information into digitized altitude data. This data is then transmitted to the control center by the transponder. Narco recommends the Model AR50 for this application.
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