MGL Avionics A16 Operating manual

MGL Avionics
A16 Aviation Audio Panel
and Razor Intercom control head
User and Installation manual

Table of Contents
FCC Statement............................................................................................................................4
General........................................................................................................................................4
Document history........................................................................................................................4
Description..................................................................................................................................4
Audio grounds.........................................................................................................................6
Audio wiring from A16 to CO microphone input..................................................................7
Audio signal flow during transmit............................................................................................9
Dual circuit intercom...............................................................................................................9
PTT behavior...........................................................................................................................9
arker beacon receiver........................................................................................................10
Power supply........................................................................................................................10
Digital control interfaces.......................................................................................................10
Audio input specifications.....................................................................................................10
Audio output specifications...................................................................................................11
Audio filters............................................................................................................................11
Power supply.............................................................................................................................11
Power supply fusing and protection......................................................................................11
Environmental qualification matrix............................................................................................12
A16 Connector pinout, Power side...........................................................................................14
A16 Connector pinout, Audio side.............................................................................................15
Typical connection diagrams.....................................................................................................16
Noise canceling inputs – how they work...............................................................................18
Control heads and options........................................................................................................20
Pinout for 3.18” Razor Intercom control head......................................................................20
Razor A16 head........................................................................................................................21
Using the A16 intercom.............................................................................................................22
Setting the volume................................................................................................................23
Audio configuration options:.................................................................................................23
Audio signal level controls....................................................................................................23
Bluetooth connectivity...............................................................................................................24
Bluetooth pairing...................................................................................................................24
Setting up microphone inputs...................................................................................................26
Adjusting VOX: .....................................................................................................................27
Adjusting Input sensitivity:....................................................................................................27
Setup of audio sources.............................................................................................................27
Assigning names to inputs....................................................................................................29
The Intercom iscellaneous menu...........................................................................................31
Signal Check.............................................................................................................................32
The Head enu........................................................................................................................33
Edit phonelist........................................................................................................................33
Set Backlight.........................................................................................................................33
Inputs....................................................................................................................................33
About.....................................................................................................................................33
A1/A2....................................................................................................................................34
aking a phone call..................................................................................................................34
The phone list............................................................................................................................36

..................................................................................................................................................36
Editing the phone list.............................................................................................................37
Cockpit voice recorder (CVR)...................................................................................................38
Electrical state interfaces..........................................................................................................39
PTT inputs.............................................................................................................................39
Accept and Hangup inputs....................................................................................................39
RS232 and CAN bus communication protocols........................................................................39
Certifications..............................................................................................................................40
echanical dimensions........................................................................................................41
aterials ..............................................................................................................................41
Dealing with common audio signal issues................................................................................42
Images.......................................................................................................................................44
Self test facility..........................................................................................................................47
Razor Firmware updates...........................................................................................................49

CC Statement
THIS DEVICE CO PLIES WITH PART 15 OF THE FCC RULES. OPERATION IS SUBJECT
TO THE FOLLOWING TWO CONDITIONS: (1) THIS DEVICE AY NOT CAUSE HAR FUL
INTERFERENCE, AND (2) THIS DEVICE UST ACCEPT ANY INTERFERENCE
RECEIVED, INCLUDING INTERFERENCE THAT AY CAUSE UNDESIRED OPERATION.
FCC ID: A8TBM62S2
NOTE: THE GRANTEE IS NOT RESPONSIBLE FOR ANY CHANGES OR ODIFICATIONS
NOT EXPRESSLY APPROVED BY THE PARTY RESPONSIBLE FOR CO PLIANCE. SUCH
ODIFICATIONS COULD VOID THE USER’S AUTHORITY TO OPERATE THE
EQUIP ENT.
General
This manual documents the installation and use of the A16 audio panel system. Please note
that operation of the audio panel is done via a connected control system such as an EFIS or
dedicated audio panel control panel or control head.
User interface varies by type of connected system. Please refer to documentation for the
connected equipment for details.
This manual describes available settings through the connected equipment in a generic way
that is applicable to all types.
Document history
8 November 2019, first release.
Description
The A16 audio panel is a split module consisting out of the audio panel system body and
optional external control. External control can take the form of one or more panel mount
control heads and/or control by an EFIS system.
The A16 audio panel provides the following functions:
a) Six independent microphone channels, each with own VOX and sensitivity settings to allow
mixed headsets. Channels can be grouped into Pilot and Passenger groups.
b) Support for two CO radios, each with audio input and output and individual PTT control.
Level control for all audio signals. Two independent Pilot and PAX PTT inputs provided. PTT
inputs dedicated to Pilot and PAX microphone circuits.
c) Support for two NAV radio audio inputs with individual level control.
d) Two independent auxiliary audio inputs with individual level control.
e) Wired stereo music input with level control – may be reassigned as two further AUX
channels.

f) Auxiliary audio output (Typical use for cockpit voice recorders etc).
e) Bluetooth mobile phone support to make and receive calls. Optional wired inputs for call
and hangup buttons.
f) Bluetooth stereo music streaming support.
g) Ability to connect to two Bluetooth devices simultaneously. Ability to automatically
reconnected to the last two connected Bluetooth devices on startup (This depends on the
Bluetooth device itself – it must allow a device initiated connection).
h) Dual circuit, stereo Pilot and PAX headset outputs.
I) Firmware updates via Bluetooth connection (requires PC or Laptop computer with Bluetooth
running Windows 7 or later).
J) Firmware update of connected Razor control head via A16 Firmware updates.
k) Communications/Control interfaces: Two RS232 ports, One CAN bus, Bluetooth SPP
profile support.
l) Built in cockpit voice recorder (CVR). This device records in an “endless tape” fashion all
microphone circuits as well as both CO radio inputs. It records about 35 minutes worth of
audio. It only records active audio, not any silence so silence periods do not use up recording
time. Recording may be played back as a block via all headset outputs or it can be extracted
in digital form via the RS232 port 1 using the supplied application from GL Avionics.

Audio grounds
In order to reduce the potential for unintended audio noise on audio wiring all audio input
circuits are based on differential grounding. This means audio inputs are not connected to the
A16 power supply grounds but are instead connected to their own audio inputs. This allows
the elimination of common mode noise as the A16 will only process differential signals.
For this purpose input grounds are grouped as follows:
1) All icrophones share a common ground.
2) All CO radios share a common audio ground
3) All NAV radios share a common audio ground
4) Wired music input has its own private ground
5) Both Auxiliary inputs each have their own private grounds.
All audio outputs are on a single shared ground but with multiple provided connections: On
the audio connector side two pins are available for audio output ground while on the power
connector a single audio output ground is provided for the auxiliary output.

In order to take full advantage of the differential input signal support both the signal wire and
the related ground wire must have the same noise profile in amplitude and time. In other
words, both connections have exactly the same unwanted signal. This is refereed to as the
common signal. The wanted signal is the difference between the signal and ground wires.
This is called the differential signal. The A16's audio inputs are designed to favor the
differential signal and reject the common signal.
It is recommended to route audio signals using shielded cables. The practice of using wire
shields as convenient ground connections is specifically discouraged. This creates ground
loops which are receivers for audio noise and makes it impossible to take advantage of the
A16's noise rejecting inputs.
The correct method to wire an audio input is to include the signal and ground as two
connections inside a shielded cable. The shield in turn connects to an independent ground.
This way the signal and signal ground will contain the same unwanted signal (noise) and this
can now be rejected by the A16.
There are various options as to what ground to use for the shields and it is not critical.
Suitable grounds are any of the A16's Audio output ground pins or a ground at the source of
the signal.
Never connect the audio cable shield at both ends of the connection. You must only connect it
on one end. This way it is not possible for any DC current or signal to flow via the shield.
Audio wiring from A16 to COM microphone input
This wired connection, in most cases will require special attention in order to prevent RF
related issues such as feedback during active TX.
A potential problem exists due to the required audio ground connection between A16 audio
panel and the CO radio. This may create a ground loop causing potentially significant
issues depending on the level of RF energy received by your aircraft's wiring during transmit.
This type of problem is typically worse on composite aircraft compared to metal skinned
aircraft.
In order to eliminate this problem the A16 provides several avenues of solutions. These are
listed here in order of preference and effectiveness:
1) Fit a 600 ohm line matching audio transformer between A16 and CO radio
microphone input. GL Avionics provides suitable high quality transformer modules.
The transformer should be fitted as close to the CO radio as possible (minimizing the
wiring length between transformer and CO radio). The transformer provides two
advantages: It completely eliminates the ground loop and provides a very effective RF
signal block (RF signals cannot pass through the transformer).
This solution is also recommended if your CO radio requires a DC load to detect a
connected microphone.
This connection is particularly recommended if your CO radio and A16 intercom are
not sharing the same power supply ground or the grounds between the two devices
are not electrically identical or contain A/C interfering signals that are not common to
both devices. Should either of these conditions exist it is recommended to use a
second transformer on the CO audio output to the A16 audio panel CO input. This
will prevent any ground potential related issues and provide the highest possible audio

quality under these conditions. Note that it may also require the use of a small low
power relay to activate the PTT on the CO radio – the relay may be driven by the A16
PTT output (please do not forget a reverse biased “snubber” diode in parallel to the
relay coil as otherwise the A16 may be damaged by the back-E F of the coil when it
deenergizes).
2) Use a two core shielded cable from A16 to CO radio and wire a 47ohm resistor
between CO radio microphone input and CO radio microphone input to ground.
The shield must be connected at the CO radio signal ground connection OR at the
A16 audio output ground connection (Never both). One of the internal shielded cores
shall be used to connect A16 audio ground to microphone ground of the CO radio
while the remaining shielded core will connect the A16 CO output to the microphone
input of the CO radio. The 47 ohm resistor should be connected at the CO radio.
Background: The 47 ohm resistor provides a very low impedance to interfering RF
signals, reducing the RF signal voltage at the microphone input. The A16 has a very
wide range output signal adjustment via a 1KOhm series output resistor. So it can
easily produce signals large enough to cater for the 20:1 loss in signal amplitude.
The 47 ohm resistor from microphone input to ground will also provide a DC path
which some radios require to detect a microphone.
3) The same as option 2 can be used if you have a CO radio that requires connection of
a dynamic microphone. In this case the resistor value should be dropped to 4.7ohm.
If your CO radio provides this (most do), reduce the microphone input sensitivity adjustment
to minimum. This also reduces the reaction of the CO radio to any interfering signals. The
A16 on the other hand provides a wide range of output signal amplitude adjustment. So the
idea is “make the CO radio as insensitive as possible” and then compensate by increasing
the output signal of the A16. This provides an easy method to increase the “signal to noise
ratio”.
If you are using a GL Avionics V16 CO radio, please use the Pilot IC input and Pilot PTT
input of the V16, leave the PAX inputs unconnected.
If you are using the supplied Bourns 5001 audio isolation transformer (recommended), the
settings are as follows: On the V16 set the Pilot IC Gain to 0.00db. On the A16 adjust the
CO output level to maximum (or near maximum). Select the CO input level to about 1/3
and the V16 RX and IC levels to about ½ of maximum.
For a direct, non isolated connection:
Using the V16 setup menu – please adjust both Pilot and PAX IC Gain to -12.00db (the
lowest setting). On the A16 – adjust the CO output level to about the 2/3 setting and the
CO input level to about 1/3. It is recommended to use the V16 VOX system at a fixed level
of “1” (do not use the bypass setting). You will be using the VOX functions of the A16 – so
leave the V16 at “1” which is just enough to switch the intercom in the V16 off when not it use.
It is advisable to wire a 100 ohm resistor (carbon type, not wound) between microphone input
and microphone ground on the V16 connector in order to lower the signal apparent
impedance and increase resistance to interference.

Audio signal flow during transmit
The A16 provides two selectable audio signal flows during active transmit. This is selected in
the Intercom setup menu of the A16 under “ iscellaneous”.
The “normal” option is: “CO sidetone from CO audio in”.
With this option selected audio flow is: icrophone → A16 → CO radio → A16 → headset.
The alternative is: “CO sidetone Intercom loop back”.
With this option selected you have two flows at the same time:
icrophone → A16 → CO radio
icrophone → A16 → Headset
Note that these settings are independent for CO 1 and CO 2 radios.
The first option will typically allow you to listen to your outgoing transmission and also help
identifying issues such as RF feedback (howling, hollow “bathroom” sound etc). The second
option can be used if your radio does not provide audio feedback during transmission.
Dual circuit intercom
The A16 provides two independent stereo output channels. These are refered as Pilot and
PAX circuit.
icrophone input ONE is always assigned to the Pilot circuit.
icrophone input TWO may be assigned to the Pilot or PAX circuit.
icrophones THREE to SIX are always assigned to the PAX circuit.
Each audio source may be assigned to either circuit or both. In addition most sources may be
assigned to either the left or right audio channel or both. For example: You may assign CO 1
to the left channel and CO 2 to the right channel if desired.
The two circuits may be operated independent or joined.
If joined, all microphone signals will be audible on both Pilot and PAX circuits. This means
Pilots and PAX may communicate with each other. All other sources however will remain at
their assignments. For example you may exclude music source from being audible on the
Pilot circuit and CO radios may not be audible on PAX circuits.
If separate, each circuit operates independent.
PTT behavior
The A16 provides two PTT inputs. PTT1 is dedicated to the Pilot circuit and PTT2 is dedicated
to the PAX circuit.
Two PTT outputs are available. PTT1 output 1 is dedicated to CO 1 and PTT2 output is
dedicated to CO 2.
It is possible to wire both PTT1 and PTT2 in parallel to a single PTT switch if this is desired.
If PPT1 is held active, only voice from the pilot circuit will be routed to the currently selected
CO radio for TX.
If PTT2 is held active, only voice from the PAX circuit will be routed to the currently selected

CO radio for TX.
If both PTT1 and PTT2 are held active then both pilot and PAX circuit will be routed to the
currently selected CO radio for TX.
Note: Only microphone signals will be routed to the CO radios. No other audio sources can
be routed to the CO radios. This includes including phone calls.
Only one CO radio can be selected for TX.
Marker beacon receiver
The A16 variant implements a 75 hz marker beacon receiver. The marker beacon antenna
is connected to pin 1 and 2 of the Power side DB25 connector. The marker beacon receiver
can be operated in a reduced sensitivity mode.
Power suppl
The A16 audio panel system is designed to be operated on a typical 12V DC aircraft power
system. The DC supply must be free of undesired transients and reasonably stable within the
acceptable supply voltage range of the A16.
It is possible to operate the A16 on 24/28V DC power supplies as well.
For operation with compromised power sources on aircraft it is advised to consider external
power conditioning such as the GL Avionics AvioGuard isolated power supply.
Digital control interfaces
The A16 audio panel provides two RS232 ports as well as a CAN bus interface.
The CAN bus is typically used with control heads from GL Avionics.
RS232 port 1 and RS232 port 2 may be used with EFIS systems. Both ports are equivalent
and can be used at the same time to two different EFIS systems.
Audio input specifications
icrophone inputs Gain range 47db For reference level:
At input sensitivity INI U setting:
0.8Vpp with 6db reserve before clipping.
At input sensitivity AXI U setting:
10mVpp.
At 75% input sensitivity (typical aviation headset
setting): 40mVpp.
Input impedance 240 ohms A/C. 8V DC microphone
bias via 470 ohms.
All other audio
inputs
Gain range 47db For reference level:
At input sensitivity INI U setting: 4.0Vpp.
At input sensitivity AXI U setting: 100mVpp.
Input impedance 250KOhm.

Audio output specifications
Output impedance 8 ohms. Suitable for connection of high impedance headphones.
Output power 0.2W low distortion. Up to 0.5W at 1% distortion.
aximum voltage
swing
5Vpp (1W into 8 ohms)
6.5Vpp into 300 ohms
Typical voltage swing
for 600 ohm aviation
headsets
1Vpp-2Vpp
Frequency response
audio power amplifier
200Hz to 20Khz at 8 ohms load, lower limit decreases with lower
loading (100uF output coupling capacitor)
Volume control range 32 steps of 3db each. Total control range = 96db.
Audio filters
icrophone inputs Pilot and PAX 350-2900Hz, Butterworth 4 pole BP
All other inputs 20-8000Hz
Power supply
The A16 is designed to operate from a 12V to 24/28V DC avionics bus. It will operate down to
8VDC. Current draw is dependent on supply voltage and drops as voltage increases
(constant power draw).
A16 supply current at 14VDC supply: 120mA typical.
Razor control supply current at 14VDC supply: 120mA typical.
Power suppl fusing and protection
The A16 and Razor control has no internal fuses. Both devices must be supplied via suitably
protected power sources to avionics standards. It is recommended that provision is made for
a maximum of 1A power draw for both devices. Both devices contain capacitors on their
power supply inputs. The Razor's capacitors have a neglible value. The A16 has a 1000uF
capacitor across its power supply input, however inrush current is limited.

Environmental qualification matrix
The environmental qualification is based on the document DO-160G
Temperature and
Altitude
4.0 Equipment Categories B2, C1
Low temperature
ground survival
4.5.1 -50°C
Low temperature
shorttime operating
4.5.1 -30°C
Low temperature
operating
4.5.2 -20°C
High temperature
operating
4.5.4 +55°C
High temperature
shorttime operating
4.5.3 +65°C
High temperature
ground survival
4.5.3 +85°C
Loss of Cooling 4.5.5 Cooling air not required Convection cooling or
forced air cooling
recommended in
compromised
installations.
Altitude 4.6.1 55,000 feet
Decompression 4.6.2 8,000 to 55,000 feet in 15 seconds
Over pressure 4.6.3 -15,000 feet
Temperature Variation 5.0 Equipment Category B
Humidity 6.0 Equipment Category A
Operational Shocks 7.2 Equipment Category B
Crash Safety 7.3 Equipment Category B Type 5
Vibration 8.0 Aircraft zone 2; type 3, 4, 5 to
category S level , type 1
(Helicopters) to category U level G
Explosion 9.0 Equipment identified as Category X

– no test required
Waterproofness 10.0 Equipment identified as Category X
– no test required
Fluids Susceptibility 11.0 Equipment identified as Category X
– no test required
Sand and Dust 12.0 Equipment identified as Category X
– no test required
Fungus 13.0 Equipment identified as Category X
– no test required
Salt Spray 14.0 Equipment identified as Category X
– no test required
agnetic Effect 15.0 Equipment tested to Category Z,
safe distance 20cm
Power Input 16.0 Equipment Category BXX
Voltage Spike 17.0 Equipment Category B
Audio frequency
conducted
susceptibility
18.0 Equipment Category B
Induced signal
susceptibility
19.0 Equipment Category AC
Radio frequency
susceptibility
20.0 Equipment Category TT
Radio frequency
emission
21.0 Equipment Category B
Lightning induced
transient susceptibility
22.0 Equipment identified as Category
B2G2L2 – no test required
Lightning direct
effects
23.0 Equipment identified as Category X
– no test required
Icing 24.0 Equipment identified as Category X
– no test required
Electrostatic
Discharge
25.0 Equipment identified as Category X
– no test required
Fire, Flammability 26.0 Equipment identified as Category C

Notes: Power input tests chapter 16. The A16 easily complies with all required criteria. The
A16 has a limitation related to power supply voltage rise time which falls well outside of any
required performance standards. Voltage rises from 0 to about 2.0V at any rate and then the
rise time to about 3.6V is very slow (in the region of greater than about 0.5 seconds) the A16
will enter self protection mode which will only be released when voltage drops again below
2.0V. In this mode the internal processor will lock itself and its integrated memories out for
protection against damage by pre-start brownout conditions. This limitation does not apply if
the A16 is already up and running and voltage dips not lower than 2.0V before rising again
slowly as the critical startup time does not apply in this case due to a secondary brownout
detection being active at this time.
The processor, should it enter self protection mode, will release this mode on the next power
cycle provided voltage ramp up is faster than the maximum time of 0.5 seconds in the
mentioned voltage range.
This limitation however is unlikely to affect any real world applications and is mentioned only
for completeness sake.
The A16 is designed not to commence operation until supply voltage reaches about 7V on
startup regardless of the above condition.
The above measures have been included to prevent any internal hardware damage due to
unusual supply voltage conditions during low to very low voltage conditions.
A16 Connector pinout, Power side
1 arker beacon antenna. 50 ohms impedance @ 75 hz.
2 arket beacon antenna ground (coax cable shield)
3 CAN-H Communications interface to a compatible GL control head
4 CAN-L As above
5 RS232 RX 1 Communications interface to an GL EFIS system
6 RS232 TX 1 As above
7 RS232 RX 2 Not used, do not connect
8 RS232 TX 2 Not used, do not connect
9 Ground for RS232 / Audio out ground
10 Auxiliary audio output
11 usic input left channel
12 usic input ground
13 Audio input right channel
14 Phone call accept button
15 Phone call reject/hangup button
16 Ground for buttons / System ground

17 PTT 1 input (Pilot PTT button)
18 PTT 1 Output to CO 1 radio
19 PTT 2 input (Copilot PTT button). Note: This input can assigned to other functions.
20 PTT 2 Output to CO 2 radio
21 Not internally connected
22 Power supply ground
23 Power supply ground (connected internally to pin 22)
24 +12V to +28V DC power supply input
25 +12V to +28V DC power supply input (connected internally to pin 24)
A16 Connector pinout, Audio side
1 icrophone 1 input
2 icrophone 2 input
3 icrophone 3 input
4 icrophone 4 input
5 icrophone 5 input
6 icrophone 6 input
7 Audio from CO 1 radio
8 Audio from CO 2 radio
9 Audio from NAV1 radio
10 Audio from NAV2 radio
11 Audio output ground
12 Pilot audio out left channel
13 Pilot audio out right channel
14 icrophone common ground
15 Auxiliary 1 audio input
16 Auxiliary 1 audio input ground
17 Auxiliary 2 audio input
18 Auxiliary 2 audio input ground
19 CO radio audio ground
20 NAV radio audio ground
21 CO 1 radio microphone input
22 CO 2 radio microphone input
23 Audio output ground

24 PAX audio out left channel
25 PAX audio out right channel
Typical connection diagrams
This diagram shows typical connection to two CO radios using the GL Avionics V16 as
example. Note that the microphone input on the radio side is connected via an audio isolation
transformer. This is highly recommended as it prevents the creation of a ground loop (the
ground connection between radio output and audio input ground on the A16 is a signal
connection and not connected to ground on the A16 side so no ground loop can be formed
here.
The audio transformer performs a secondary task of providing a very effective block for RF
signals preventing RF feedback issues. RF feedback can otherwise become troublesome as
typically a large network of wiring connects to the A16 intercom providing a receive path for
RF signals that can couple into the radio's microphone input and cause a feedback loop. The
A16, as packaged, contains two specially selected audio transformers for this purpose. These
are chosen for their excellent RF blocking performance. They should be wired as shown in
the diagram – the wired connection between the radio and the transformer should be kept
very short. If short, it is not required to use shielded cable for this side.

Note that all shielded cable only connects the shield at one end. This way no signal travels on
the shield itself.
Note that the CO radio audio ground (pin 19 on the A16) is not an electrical ground. This is
a signal input forming part of the noise canceling system. Do not use this connection as
grounding point for a shield.
When wiring headset sockets please ensure that the sockets are isolated from any metal
panels and isolated from each other. Headset and microphone grounds must not be shared.
You must not route microphone signal wires and headset signal wires in the same shielded
cable unless the signals are also shielded from each other. It is otherwise possible to create
an unintentional audio feedback path from headset to microphone via capacitive and inductive
coupling between the wires. This can cause howling at higher volume levels.
Please never use shields as signal conductors. Shields must be connected to an electrical
ground point or dedicated audio ground.
Never use noise canceling audio signal grounds on the A16 as shield ground points.
Audio noise canceling grounds on the A16 are:
CO Ground, pin 19.
NAV Ground, pin 20.
AUX1 Ground, pin 16.
AUX2 Ground, pin 18.
USIC ground, pin 13 (also AUX3 and AUX4 ground).
Ground points that are referenced to ground and that may be used as shield grounds for their
respective signals:
IC ground, pin 14.

Audio out ground pins 11 and 23.
System Ground, pin 12.
Antenna Ground, pin 2.
Audio out ground, pin 9.
Noise canceling inputs – how the work
Normally, an audio input “sees” the signal as the voltage difference between its input and the
electrical ground of its own circuit. Should the audio source have a slightly different ground
are there is noise that is different at the source ground compared to the A16 ground then this
difference will add to the signal.
To prevent this from happening the A16 employs a number of virtual ground points that feed
into a differential amplifier that only sees the difference between the two signals. One of the
signals is the normal audio signal from the source and the other is the ground at the source.
The A16 thus sees the signal as it is created at the source and any differences between
source and A16 ground are canceled.
In cases were this is not needed, please connect the relevant signal ground on the A16 to any
A16 audio output ground or the IC ground (pin 14).
Audio signal
Audio signal reference
(audio ground from source)
Signal seen by A16 is
Difference between Audio
signal and ground at the
audio signal source

Example connection of two NAV radios.

Control heads and options
The A16 module must be connected to at least one controller. A controller is typically a Razor
head (more than one may be connected) or an EFIS system.
Pinout for 3.18” Razor Intercom control head
1 Supply +9 to +28VDC
2 Supply ground
3 RS232 RX Port 1
4 RS232 TX Port 1
5 RS232 RX Port 2