AXP340 Transponder Installation Manual
10 March 2014
01201-00
Issue AF
AVIDYNE CORPORATION
Page 11
5.5 Interface Details
5.5.1
Power Input
The power supply can be 11-33 Volts DC; no voltage adjustment is required. Contacts 11 and 12 on the 24
way connector are both available as power inputs. This is for compatibility reasons only – internally the
two are connected together, and in most installations only one need be connected to the power supply.
Use a 3 Amp circuit breaker for power supply protection to the AXP340.
5.5.2
Lighting Bus Input
Two lighting bus inputs are provided on the 24 way connector to accommodate aircraft with 14 Volt or 28
Volt lighting systems. When the lighting bus operates at 28 Volts, connect the bus input to contact 3, and
leave contact 2 unconnected. When the lighting bus operates at 14 Volts, connect the bus input to contact 2.
In this case contact 3 can be left unconnected, but for backwards compatibility may also be grounded
instead with no effect.
The operation of the lighting bus input is determined by the value of the lighting control setting in section
6.1.16.
5.5.3
Mutual Suppression
Mutual suppression allows two or more transmitters on adjacent frequencies to inhibit the other transmitters
when one is active to limit the interference effects. It is commonly used between transponders and DME
systems, and between transponders and collision avoidance systems.
The AXP340 provides two styles of mutual suppression interface on the 24 way connector. The Suppress
input on contact 9 is typically used in aircraft with simple DME systems and no other suppression
requirements. It is an input only, and is active whenever the input is greater than approximately 5 Volts.
The Suppress I/O on contact 4 is an ARINC compatible suppression bus interface, which acts as both an
input and an output. The AXP340 will assert this signal when it is transmitting, and can be suppressed by
other equipment that asserts the signal. The AXP340 will drive approximately 24 Volts on the output
(independently of supply voltage), and will treat the input as active whenever the bus has greater than 10
Volts.
5.5.4
Altitude Inputs and Output
The AXP340 can use either a parallel Gray code altitude input, or serial RS232 altitude input. Both of these
interfaces are on the 24 way connector. If the altitude encoder you are using offers both, we recommend
using the RS232 serial input. Serial formats allow a higher resolution altitude representation that can be
