IRT AA-704 User manual

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IRT Eurocard
Type AA-704 & AA-704T
Audio Distribution Amplifier
Designed and manufactured in Australia
I R T Electronics Pty Ltd A.B.N. 35 000 832 575
26 Hotham Parade, ARTARMON N.S.W. 2064 AUSTRALIA
National: Phone: [phone] Fax: [phone]
International: [phone] [phone]
Email: [e-mail]

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IRT Eurocard
Type AA-704 & AA-704T
Audio Distribution Amplifier
Instruction Book
Table of Contents
Section Page
General description 3
Technical specifications 5
Technical description 6
Internal adjustments 7
Configuration 8
Installation 9
Operational safety 9
Pre-installation 9
Installation & connection 10
RCA phono rear assemblies - RB704 & RB-367 10
Front and rear location diagrams 11
Sub-modules 13
CAA-3131 Remote gain control 13
AG-604SW Switched frequency oscillator 15
AG-604ST Stereo oscillator 18
AS-604 Remote mode control 20
Drawing list index 23
This instruction book applies to units later than S/N 9404000.

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IRT Eurocard
Type AA-704 & AA-704T
Audio Distribution Amplifier
GENERAL DESCRIPTION
The IRT AA-704 is a high performance Audio Distribution Amplifier which is manufactured on extended Eurocard
boards. A total of 12 cards and a PT-700 Dual 28 Vac power module can be accommodated in an IRT FR-700
3 Rack Unit Frame.
Other mounting options are available including the FR-722 1 Rack Unit Chassis/PSU conversion and special
frames for Telecom use.
The AA-704T is a special version of the AA-704 for Telecom use and is supplied with rear assembly type RB-733T.
Except where noted all references to the AA-704 in this instruction book apply equally to the AA-704T.
The AA-704 can be used for either mono or stereo signals, a simple on board jumper change is all that is required
to vary the mode of operation.
Front panel access is provided for the gain adjustment of Mono/Left and Right Channels. A green power on LED
indicates the presence of both the supply rail voltages.
There are three internally selectable gain ranges, + 6 dB, + 12 dB, + 18 dB. The variable gain control provides
adjustment from zero output to the maximum of the selected gain range.
The maximum output of the AA-704 is + 24 dBu.
The amplifier has space to accept plug in sub-module options:
AR-604:- Remote Gain and Control module.
AG-604SW:- Four Frequency Switched Oscillator module.
AG-604ST:- FACTS stereo oscillator module. Left continuous & right interrupted.
AS-604:- Stereo /mono and phase control module.
Standard features:
• Selectable stereo or mono mode.
• Ten outputs mono or five left and five right in stereo.
• Up to 12 ADA's per frame.
• Dual redundant low voltage AC supplies.
• Input common mode rejection.
• High impedance balanced or unbalanced, bridging input.
• Balanced 40 Ohm output source impedance.
• Three internally selected gain ranges +6 dB, +12 dB and +18 dB.
• Front panel left & right gain adjustment.
• Maximum output level +24 dBu.
• Excellent electrical characteristics.
Equipment provided:
AA-704: AA-704 Audio Distribution Amplifier module.
RB-733 Rear Assembly
or
AA-704T: AA-704T Audio Distribution Amplifier module.
RB-733T Rear Assembly
Optional: RB-704 Rear Assembly (RCA phono)

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Accessories available:-
FR-700 Eurocard module mounting frame:- Provides mounting for up to 12 AA-704 amplifiers
and one PT-700 Dual AC power supply side by side
in 134 mm of standard Rack space (3 Rack Units).
FR-722 1 RU chassis conversion/PSU The FR-722 provides a means of converting
Eurocards to a 1 rack unit format. The FR-722 can
be fitted with either one or two Eurocards in a
horizontal side by side format. A single AC power
supply is included to power the cards.
AR-604 Remote gain control. The AR-604 can be used for the remote gain
control or by varying the strapping on the board can
provide stereo panning, audio over control and cross
fading.
AG-604SW Four frequency switched oscillator module The AG-604SW provides a remotely switchable
fixed 400 Hz, 1 KHz, 4 KHz or 10 KHz tone signal.
AG-604ST FACTS stereo oscillator module The AG-604ST provides a continuous 1 KHz tone
signal on the left channel and the same signal
interrupted every second on the right channel.
AS-604 Remote mono/stereo & phase control. The AS-604 can be to remotely switch between
mono and stereo modes or to reverse the phase of the
left channel in stereo mode. Links on the board allow
a choice of either a -3 dB or -6 dB mono mix.
TME-6 Eurocard extender board.
Instruction Book.

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TECHNICAL SPECIFICATIONS
IRT Eurocard module type AA-704
Inputs: Left/Mono and Right
Type Tranformerless, bridging.
Impedance AA-704 > 10 KΩ.
AA-704T 600 Ωor > 10 KΩselectable by links on RB-733T.
Max. input level +24 dBu ( 6 dB gain mode )
Input CMR > 55 dB 20 Hz to 20 KHz
Outputs:
Type Transformerless, balanced.
Number RB-704, RB-733 & RB-733T 10 (10 mono or 5 left and 5 right).
RB-367 26 (26 mono or 13 left and 13 right).
Impedance RB-733 & RB-733T < 40 Ω.
RB-704 & RB-367 ≈560 Ω.
Max. output level +24 dBu into 10 loads each 600 Ω.
DC on output < ±20 mV.
Performance:
Gain Internally linked to a maximum gain of + 6, + 12 or +18 dB.
Frequency response + 0 / - 0.3 dB for 20 Hz to 20 KHz.
Harmonic distortion < 0.005% 20 Hz to 20 KHz at +20 dBm.
Noise -110 dB, Ref. +24 dBm 20 Hz to 20 KHz.
Crosstalk;
Left/right -75 dB 20 Hz to 20 KHz.
Amplifier/amplifier -80 dB 20 Hz to 20 KHz.
Power Requirements: 28 Vac CT (14-0-14) or ±16V DC
Power consumption 55 mA ( no signal )
to
170 mA ( + 20 dBu, all outputs loaded in 600 Ω).
Connectors:AA-704: Plugable screw block connectors (RB-733)
AA-704T Krone IDC (RB-733T)
Optional RCA phono (RB-704 or RB-367)
Other:
Temperature range 0 - 50° C ambient
Mechanical Suitable for mounting in IRT 19" rack chassis types FR-700 &
FR-722 with input output and power connections on the rear panel
Finish: Front panel Grey enamel, silk screened black lettering & red IRT logo
Rear assembly Detachable silk screened PCB with direct mount connectors to
Eurocard and external signals
Dimensions 6 HP x 3 U x 220 mm IRT Eurocard
Standard accessories AA-704: RB-733 Rear connector assembly with plugable compression screw
terminals. Matching connectors for audio inputs & outputs
supplied.
AA-704T: RB-733T Rear connector assembly with Krone IDC terminals.
Optional accessories RB-704 Rear connector assembly with 10 x RCA phono
connectors.
RB-367 Rear connector assembly with 26 x RCA phono
connectors.
TME-6 module extender card

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TECHNICAL DESCRIPTION
The block diagram (ref.. 802827) shows that the AA-704 comprises:-
a) Two separate input stages, "Left" and "Right. Each input stage converts its balanced high impedance input to an
unbalanced low impedance output. The gain of these stages can be varied by 12 dB in two 6 dB steps by
changing the stage gain links.
b) A single optional 'plug-in' area. Should a plug-in option be installed Links 1 and 2 should be cut.
c) Two front panel adjustable gain controls. Links are provided after the gain controls to feed the Left or Right input
to both output stages for Mono operation, or the Left input to the Left output and the Right input to the Right
output for stereo.
d) Two separate output stages. Each converts its unbalanced input to 5 resistively isolated balanced outputs.
e) Power Supply:- See detailed description following.
Power supply:
Input power to the module may be fed by a number of means.
1. One or two 14 - 0 - 14 Vac supplies via connections on the 64 pin DIN rear connector of the module.
(Used when module is mounted in FR-700 chassis or FR-748A chassis fitted with one or two PT-701
PSU’s.)
2. Two ±16 Vdc supplies via connections on the 64 pin DIN rear connector of the module. (Used when
module is mounted in FR-748A chassis fitted with one or two PT-748A PSU’s.)
3. One 14 - 0 - 14 Vac supply and one ±16 Vdc supply via connections on the 64 pin DIN rear connector of
the module. (Used when module is mounted in a FR-748A chassis fitted with 1 x PT-701 PSU and 1 x
PT-748A PSU.)
4. A single 14 - 0 - 14 Vac supply connected to SK 2 on the rear assembly. (Used when module is mounted
in FR-722 chassis.)
The input power is isolated by fusible resistors F 1 to F 4. Should these fail they should be only replaced by a similar
type of the same value or protection of the common power supply will be compromised.
If an AC supply is provided, the isolated AC is full wave rectified by diodes D 1 to D4 and D5 to D 8 to provide a
raw DC voltage of approximately 20 V at filter capacitors C 15 and C 16. The actual voltage will vary depending on
the type of frame, loading of PSU by other modules and the local mains supply voltage.
If a DC supply is provided, the isolated DC passes through the diodes D 1 to D4 and D5 to D 8 which provide
protection against accidental reverse polarity connection of the DC supply. Where a DC supply is used the input
voltage must be at least ±15 Vdc under all conditions to ensure sufficient margin for the proper operation of the
following voltage regulators and losses in the input fusible resistors and diodes.
The raw DC power is fed to three terminal regulator IC’s which provide ±12 Vdc rails for the operating circuits.
The LED on the front panel is wired in series with a zener diode between +12 and -12 Volts. The zener is to ensure
that the LED extinguishes if either one of the regulators fails.
Wideband modification:
(For use with timecode, composite stereo and other extended frequency response signals.)
Capacitors C 11 & C 13 in the feedback loops of U 3A & U 4A respectively provide high frequency rolloff above 20
KHz. If a higher frequency response is required the value of C 11 & C 13 may be decreased from 120 pF to 22 pF.
This will provide a useful response to 100 KHz ±0.5 dB.

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AA-704 Internal Adjustments
The following adjustable resistors are factory set and should not be adjusted unless a component has been changed.
They are not 'operational' controls. Before adjusting any of these controls allow time for the AA-704 to reach
temperature stability.
RV 1 "Left' Common Mode Rejection.
Adjusted to reduce input common mode signals to a minimum at the output of the AA-704.
RV 2 "Right' Common Mode Rejection.
Adjusted to reduce input common mode signals to a minimum at the output of the AA-704.

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CONFIGURATION
The AA-704 may be configured for several modes of operation including remote control and conversion to a multi
output oscillator with the addition of sub-modules. This is achieved by various link settings as outlined below.
The AA-704 is normally delivered set for stereo operation, 6 dB maximum gain on both channels and no
sub-modules fitted.
Note: AA-704T fitting of sub-modules.
The RB-733T is supplied without a connector for remote control of sub-modules. If a sub-module is to be fitted that
requires remote control a 3 pin polarised header type 1100-8-103-01 should be fitted to the RB-733T PCB in the
position provided between the left and right input sockets.
Configuration Summary:
1. Sub-modules: No sub-module LK 1 & LK 2 soldered on board.
Any sub-module: Cut LK 1 & LK 2 on board.
AR-604 Set to stereo mode as below.
AG-604SW Set to L mono mode as below. LK 7 & LK 8 are inoperative.
AG-604ST Set to stereo mode as below. LK 7 & LK 8 are inoperative.
AS-604 Set to stereo mode as below.
2. Stereo/mono: Stereo LK 3 & LK 6 installed. LK 4 not installed.
Mono L Input LK 3, LK 4 & LK 5 installed. LK 6 not installed.
LK 8 sets maximum gain. Gain adjust is only by RV 3 L gain.
LK 7 and RV 4 are inoperative.
Mono R Input LK 3, LK 5, & LK 6 installed. LK 4 not installed
LK 7 sets maximum gain. Gain adjust is only by RV 4 R gain.
LK 8 and RV 3 are inoperative.
3. Maximum gain: Left channel LK 8 set as designated on PCB overlay for +6, 12 or 18 dB max.
Right channel LK 7 set as designated on PCB overlay for +6, 12 or 18 dB max.
Sub-module
area
RV 3 Left Gain
RV 4 Right Gain
L
K
3
LK 6
LK 1
LK 2
PCB 802736
PC Board Layout
Relative Position of User Settings
(Not to scale) Rear
Assembly
F
R
O
N
T
P
A
N
E
L
L
K
4
L
K
5
L
K
7
L
K
8

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INSTALLATION
Operational Safety
Pre-Installation
Handling:
The modules used in this equipment contain static sensitive devices and proper static free handling precautions
should be observed.
Where individual circuit cards are stored, they should be placed in antistatic bags and proper antistatic procedures
should be followed when inserting or removing cards from these bags.
Power:
AC mains supply: Ensure that operating voltage of unit and local supply voltage match and that correct rating fuse
is installed for local supply.
DC supply: Ensure that correct polarity is observed and that DC supply voltage is maintained within the
operating range specified.
Earthing:
AC mains supply: Chassis earth connection of the equipment is via the earth connection on the three pin mains
input. This is a safety earth and must be connected.
DC supply: Chassis earth connection of the equipment is via the positive terminal on the DC input. The DC positive
supply should be connected to earth at the supply . A separate chassis earth connection is available on the centre
connector of the DC input connector which may be connected if desired.
Signal earth:
Balanced audio signal Pin 1 of connector is connected to PSU earth for shielding purposes only.
Unbalanced audio signal outer of RCA phono connector is connected to PSU earth.
It is strongly recommended that where double insulated equipment is
being used that a proper connection be made between the signal earth and
true ground earth at some point in the external circuit.
WARNING
Operation of electronic equipment involves the use of voltages and currents which
may be dangerous to human life. Maintenance personnel should observe all safety
regulations. Do not change components or make adjustments inside the equipment
with power ON unless proper precautions are observed. Note that under certain
conditions dangerous potentials may exist in some circuits even though power
controls are in the OFF position.

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Installation in frame or chassis:
See details in separate section for selected frame type.
Note: Fitting AA-704T with RB-733T into FR-722.
No AC input plug is provided on the rear of the RB-733T PCB and the AC input must be provided direct to the
AA-704T main module PCB. This is accomplished by fitting a 3 pin polarised header type 1100-8-103-01 to the
main PCB in the position provided next to AC input fuses FS 1 & FS 2.
RCA phono rear assemblies:
Types RB-704 - 10 output & RB-367 - 26 output.
Two types of rear assemblies are available with RCA phono connectors for use with domestic style equipment such
as VHS machines where only unbalanced connections are provided.
Each is equipped with RCA connectors on all outputs with red and black bodies used to distinguish between left and
right channels.
The two inputs may be equipped with either RCA phono connectors (for unbalanced input) or a 3 way Phoenix
connector block ( for either balanced or unbalanced input). Where the input is unbalanced the gain of the amplifier
will be reduced by 6 dB and so the gain setting link for each channel should be adjusted to the next higher setting
(normally from 6 dB, factory set, to 12 dB). See Configuration for details.
Where the rear assembly is equipped with the 3 way balanced Phoenix input connector it may be used for either
balanced or unbalanced signal input. When unbalanced signals are used they may be connected either between the
+ input and - input or between the + input and Gnd terminals.
If connection on the RB-704 is made between the + input and - input then a slight improvement in noise performance
may be achieved by fitting a 1K Ohm resistor between the -°input and Gnd on the connector. The RB-367 is factory
fitted with these resistor s (R 1 & R 2 located next to input connectors) and these may be removed if balanced input
operation is required.
RB-367 only:
The RB-367 may only be fitted to IRT 1 RU Eurocard frames such as the FR-722A. The frame can only
accommodate one AA-704 with the RB-367 as the RB-367 covers the entire rear of the frame.
The AA-704 module must be mounted on the right hand side of the frame (next to the power switch) and a blank
front panel should be secured in the unused position on the left hand side.
Audio Connections:
For mono operation it is usual to connect the input audio cable to the Left input pins. For stereo connect the Left
input cable to the Left input and the Right input audio cable to the Right input.
If input termination is required on the RB-733 then termination resistors should be fitted to the input sockets.
The RB-733T is fitted with 620 Ωtermination resistors as standard with a link provided in series with the
termination which should be removed if loop through or high input impedance operation is required. (The 620 Ω
resistrors in parallel with the normal high input impedance provide an actual input impedance of 600 Ω.)
Connect as many outputs as required. Remember for stereo operation to observe the polarity markings on the rear
assembly.
See also special comments above concerning RCA phono rear assemblies types RB-704 and RB-367.

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The following front panel and rear assembly drawings are not to scale and are intended to show approximate layout
& connection order only.
GAIN
L
R
AA-704
DC
RB-733
Remote
1 2 3
LEFT
& MONO
INPUT RIGHT
INPUT
L O/P’s R O/P’s
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
RB-733
LEFT
& MONO
INPUT RIGHT
INPUT
L O/P’s R O/P’s
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
-
+
Gnd
Remote
1 2 3
600 Ohm 600 Ohm

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Rear assemblies with RCA type
output connectors. Note input
connectors may be either RCA
unbalanced or Phoenix balanced
type.
LEFT
& MONO
INPUT RIGHT
INPUT
Remote
1 2 3
L O/P’s R O/P’s
L O/P’s R O/P’s
RB-367
-
+
Gnd
-
+
Gnd
RB-733
-
+
Gnd
-
+
Gnd
LEFT
& MONO
INPUT RIGHT
INPUT
Remote
1 2 3
L O/P’s R O/P’s
LEFT
& MONO
INPUT RIGHT
INPUT
Remote
1 2 3
L O/P’s R O/P’s
L O/P’s R O/P’s
RB-367
RB-733
LEFT
& MONO
INPUT RIGHT
INPUT
Remote
1 2 3
L O/P’s R O/P’s

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IRT Eurocard Sub-board
Type CAA-3131
GENERAL DESCRIPTION
This plug-in option for selected IRT audio distribution amplifiers can be configured to provide one of the following
modes of operation:
• STEREO FADE over 75 dB range
• STEREO TRIM of 6 dB
• CROSS FADE over 75 dB or 6 dB range
• MIX L+R & FADE both by up to 75 dB.
Only one mode of operation is possible at any time.
TECHNICAL SPECIFICATIONS
IRT Eurocard Sub-module
Type CAA-3131
Control input:
Remote gain component 100 KΩpotentiometer (Not supplied)
Connections: On rear assembly of main module
3 pin female polarised IDC # 1300-103-426
Pin 1 CCW connection of the potentiometer (GND)
2 Rotor
3 CW connection (1 KΩin series with + 12 Vdc)
Performance:
(See main module specifications for other specifications)
Frequency Response +0 / -0.5 dB 20 Hz to 20 KHz.
Harmonic Distortion < 0.1% 20 Hz to 20 KHz at +20 dBm.
Noise -100 dB, Ref. +24 dBm 20 Hz to 20 KHz.
Attenuation > 75 dB.( Measurement for stereo fade mode )
Power requirements: ±12 Vdc from main module
Power consumption See main module specifications
Other:
Temperature range 0 - 50° C ambient
Dimensions 65 mm x 48 mm
Standard accessories Matching connector for control input type:
1300-103-426
Optional accessories Instruction manual.
CIRCUIT DESCRIPTION
The circuit uses a TDA1074A variable gain control IC to perform the configured function. Configuration is by
means of resistors which determine the function as shown on diagram 802739.
The input control circuit is isolated from the signal path and uses DC control which is filtered by the combination of
R 2 & C 1 to provide immunity to noise, either in the external wiring or in the operation of the external
potentiometer.
The operating range is determined by the type of cable used and the degree of noise in the environment.
For best results over long distances a low loss screened cable should be used and the route carefully chosen to avoid
proximity to high level noise sources.
For short distances flat IDC ribbon cable will suffice.

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CONFIGURATION
The main module must first be configured to accept the sub-module. This is achieved by various link settings as
outlined in the main module manual.
The main module is normally delivered set for stereo operation and no sub-modules fitted. Before installing the
CAA-3131 set the main module to stereo mode as detailed in main module instruction manual.
The AA-604 can be configured to provide one of the following modes of operation:-
1. Stereo Fade Up to 75 dB attenuation on both channels simultaneously.
2. Trim As above, but range limited to 6 dB.
3. Cross Fade Fade down left, fade up right/ fade down right, fade up left. Up to 75 dB range.
4. Balance As above but range limited to 6 dB.
5. Mix L+R & Fade Add left to right and fade both by up to 75 dB.
To configure these options see Drawing 802739.
INSTALLATION
Module
To install the sub-module onto the main module first ensure that the proper mode of operation has been selected on
both the main and sub-modules.
Then remove straps LK 1 and LK 2 on the main module.
Hold the sub-module so that the legends on the sub-board and the legends on the main module have the same
orientation.
Place the sub-module over the connector pins of the main module. The 16 pins fit into 16 holes in the sub-module.
Push the sub-board down until it rests on the orange insulation of the pins.
Remote control
To control the gain a remote 100 KΩvariable resistor should be wired between the pins marked Remote "1", "2" and
"3" on the main module rear assembly.
Connect Pin 1 to the bottom of the potentiometer (CCW connection)
Pin 2 to the slider (rotor connection)
Pin 3 to the top (CW connection).

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IRT Eurocard Sub-module
Type AG-604SW
GENERAL DESCRIPTION
The AG-604SW Four frequency switched oscillator sub-module converts the supporting main module audio
distribution amplifier into a multi output reference oscillator for test or alignment purposes.
Provision is made to remotely switch the frequency to a fixed 400 Hz, 1 KHz, 4 KHz or 10 KHz tone.
TECHNICAL SPECIFICATIONS
IRT Eurocard Sub-module
Type AG-604SW
Control input:
Remote switch component Single pole 4 position or equivalent (Not supplied)
Connections: On rear assembly of main module
3 pin female polarised IDC # 1300-103-426
Pin 1 GND
2 Relay 1 control
3 Relay 2 control
Performance:
(See main module specifications for other specifications)
Distortion < 0.01% at + 8 dBm.
Frequency Remote selectable to:
400 Hz, 1 KHz, 4 KHz or 10 KHz.
Power requirements: ±12 Vdc from main module
Power consumption See main module specifications
Other:
Temperature range 0 - 50° C ambient
Dimensions 65 mm x 48 mm
Standard accessories Matching connector for control input type:
1300-103-426
Optional accessories Instruction manual.

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CIRCUIT DESCRIPTION
The circuit comprises of a low distortion Wein bridge oscillator with a remote control facility to select the operating
frequency.
The normal input circuitry of the distribution amplifier is not used.
Control of frequency is by way of grounding contacts which activate relays on the sub-board to select the correct
time constants in the circuit. These are arranged so that four commonly used frequencies may be obtained using only
two control relays operated over a three wire circuit.
The output from the oscillator is fed to the left output gain control on the main circuit board which provides a single
level control for all outputs.
The circuit does not contain a latch for the remote input and the external contact must therefore be maintained for as
long as the selected frequency is required.
In the absence of any remote input both relays will turn off and the oscillator will default to 1 KHz.
CONFIGURATION
The main module must first be configured to accept the sub-module. This is achieved by various link settings as
outlined in the main module manual.
The main module is normally delivered set for stereo operation and no sub-modules fitted. Before installing the
AG-604SW set the main module to L mono mode as detailed in main module instruction manual. LK 7 & LK 8 are
inoperative.

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INSTALLATION
Module
To install the sub-module onto the main module first ensure that the proper mode of operation has been selected on
both the main and sub-modules.
Then remove straps LK 1 and LK 2 on the main module.
Hold the sub-module so that the legends on the sub-board and the legends on the main module have the same
orientation.
Place the sub-module over the connector pins of the main module. The 16 pins fit into 16 holes in the sub-module.
Push the sub-board down until it rests on the orange insulation of the pins.
Remote control of frequency
The frequency of the oscillator may be set using the remote connector on the rear assembly of the main module.
If no connection is made the oscillator will default to 1 KHz operation.
As the remote switches and wiring carry the full relay current it is important that the losses in the external wiring be
kept to a minimum.
No damping of the remote selection is provided and some instability of the output signal will result during switching.
This should be considered when choosing the type of switch and when it will be operated.
Refer to Drawing 803006 for modes of operation.
Frequency Connect to Pin 1 (GND)
400 Hz 2
1 KHz Default N/C
4 KHz 2 & 3
10 KHz 3

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IRT Eurocard Sub-board
Type AG-604ST
GENERAL DESCRIPTION
The AG-604ST provides a continuous 1 KHz tone signal on the left channel and the same signal interrupted every
second on the right channel.
This configuration conforms to the recommended practice of FACTS (Federation of Australian Commercial
Television Stations) for channel identification.
TECHNICAL SPECIFICATIONS
IRT Eurocard Sub-module
Type AG-604ST
Performance:
(See main module specifications for other specifications)
AG-604ST FACTS stereo oscillator module:
Distortion < 0.01% at + 8 dBm.
Frequency 1 KHz continuous left channel
1 KHz interrupted every second right channel
Power requirements: ±12 Vdc from main module
Power consumption See main module specifications
Other:
Temperature range 0 - 50° C ambient
Dimensions 65 mm x 48 mm
Optional accessories Instruction manual.
CIRCUIT DESCRIPTION
The normal input circuitry of the distribution amplifier is not used.
The circuit comprises of a low distortion Wein bridge oscillator, an astable multivibrator and a voltage controlled
switch.
The oscillator output is passively split with one output fed directly to the left output.
The other output is fed via an FET which is gated on and off by a square wave oscillator to provide an output which
is alternatively on and off. This if fed to the right output.
The gating frequency may be trimmed by adjusting potentiometer RV 1 which sets the frequency of the astable
multivibrator U 2.
The outputs from the oscillator sub-board are fed directly to the left and right output gain controls on the main circuit
board which provides level control for the left and right outputs respectively.

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CONFIGURATION
The main module must first be configured to accept the sub-module. This is achieved by various link settings as
outlined in the main module manual.
The main module is normally delivered set for stereo operation and no sub-modules fitted. Before installing the
AG-604ST check that the main module is set to stereo mode as detailed in main module instruction manual.
Note that LK 7 & LK 8 are inoperative.
INSTALLATION
Module
To install the sub-module onto the main module first ensure that the proper mode of operation has been selected on
the main module.
Then remove straps LK 1 and LK 2 on the main module.
Hold the sub-module so that the legends on the sub-board and the legends on the main module have the same
orientation.
Place the sub-module over the connector pins of the main module. The 16 pins fit into 16 holes in the sub-module.
Push the sub-board down until it rests on the orange insulation of the pins.

0704-aa.ibw.doc page 20 of 23 25/05/98
IRT Eurocard Sub-board
Type AS-604
GENERAL DESCRIPTION
The AS-604 can remotely switch between mono and stereo modes or reverse the phase of the left channel in stereo
mode. Links on the board allow a choice of either a -3 dB or -6 dB mono mix. :-(Only one mode is possible at any
time.)
1. Normal stereo operation.
2. Reverse phase of left channel
3. Switch left channel input to mono output.
4. Mix left and right channels to mono output with selectable 3 dB or 6 dB cut in signal level.
TECHNICAL SPECIFICATIONS
IRT Eurocard Sub-module
Type AS-604
Control input:
Remote gain component (Not supplied)
Connections: On rear assembly of main module
3 pin female polarised IDC # 1300-103-426
Pin 1 GND
2 Relay 1 control
3 Relay 2 control
Performance:
(See main module specifications for other specifications)
Operation modes Remote selectable:
(Only one mode is possible at any time)
Stereo (normal)
Invert left channel phase
Mono output from left input
Mix of stereo input to mono output
Frequency Response +0 / -0.5 dB 20 Hz to 20 KHz.
Distortion < 0.1% at +20 dBm.
Noise -100 dB wrt +24 dBm.
Attenuation mono mix mode -3 dB or -6 dB selectable by links.
Power requirements: ±12 Vdc from main module
Power consumption See main module specifications
Other:
Temperature range 0 - 50° C ambient
Dimensions 65 mm x 48 mm
Standard accessories Matching connector for control input type:
1300-103-426
Optional accessories Instruction manual.