IRT VA-700 User manual

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Revision 10
Analogue Video Distri ution Amplifier
User Manual

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 2 of 23 Revision 10
ANALOGUE VIDEO DISTRIBUTION AMPLIFIER
Revision istory:
Revision Date By Change Description Applicable to:
01 21/03/1996 AJP Original Issue. S/N ≥ 9500000
02 02/07/1996 AJP AVD-3120 su -document included. S/N ≥ 9500000
03 25/07/1996 AJP Front & rear panels redrawn to scale with handle
omitted.
S/N ≥ 9500000
04 27/11/1996 AJP CVA-3120 su -document included. S/N ≥ 9500000
05 12/01/2001 AL IRT Border page added for PDF format,
00COMMON.doc file contents added
S/N ≥ 9500000
06 05/07/2002 AL Link paths reset S/N ≥ 9500000
07 11/09/2002 AL Drawing list updated and all relevant test
procedures (hidden) added.
S/N ≥ 9500000
08 22/10/2010 AL O solescence of su - oard information noted, test
procedures (hidden) removed.
S/N ≥ 9500000
09 22/05/2012 AL Reformatted layout. S/N ≥ 9500000
10 21/09/2015 AL Upgraded to I.R.T. Communications company name. S/N ≥ 9500000

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 3 of 23 Revision 10
USER MANUAL
Table of Contents:
Section Page
Revision History 2
Operational Safety 4
General Description 5
Technical Specifications 6
Configuration 7
Location of links & user settings 8
Installation 9
Front and rear layouts 10
Su -modules (NOTE: Obsolete – No Longer Available. Information for existing modules only) 11
DL-700 Delay & filter su -module 11
General Description 11
Technical Specifications 12
Configuration 13
Installation 13
AVD-3120 Video sync failure detector 14
General Description 14
Technical Specifications 15
Configuration 16
Installation 16
CVA-3120 Remote gain control 17
General Description 17
Technical Specifications 18
Configuration 19
Installation 20
EQ-1227 Equaliser su - oard 21
General Description 21
Technical Specifications 21
Installation 22
Maintenance & Storage 23
Warranty & Service 23
Equipment return 23
This instruction ook applies to Serial Num ers ≥ 9500000.

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 4 of 23 Revision 10
OPERATIONAL SAFETY
WARNING
Operation of electronic equipment involves the use of voltages and currents that
may e dangerous to human life. Note that under certain conditions dangerous
potentials may exist in some circuits when power controls are in the OFF position.
Maintenance personnel should o serve all safety regulations.
Do not make any adjustments inside equipment with power ON unless proper
precautions are o served. All internal adjustments should only e made y suita ly
qualified personnel. All operational adjustments are availa le externally without
the need for removing covers or use of extender cards.

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 5 of 23 Revision 10
GENERAL DESCRIPTION
The VA-700 is a video distri ution amplifier of modular Eurocard construction having facilities for ca le
equalisation, longitudinal hum reduction, and clamping.
The input is a ridging loop through type to facilitate connection to other equipment. Ten 75 Ω outputs are
provided on the rear with an additional output on the front panel for ease of monitoring.
The input and output grounds are separated to provide rejection of longitudinally developed hum. The input is AC
coupled and the output DC restored with options for no clamping or clamping to the internal or an external signal.
The external clamping facility may e used to provide correct DC restoration in YUV & RGB signal situations.
The video gain may e varied y ± 3 dB from the front panel. Internal preset controls allow adjustment of the
amplifier frequency response, optimisation of the longitudinal hum rejection, and stage output DC voltages.
Ca le equalisation is provided for up to 300 metres of 75 Ω high quality ca le with adjustment via the front panel.
The VA-700 may also e used as a pulse distri ution amplifier. (Only 6 outputs may e used for 4 Vp-p)
The VA-700 is manufactured on an extended Eurocard oard for mounting in IRT Eurocard frames.
Standard features:
• IRT Eurocard construction
• Loop through input
• Ten BNC outputs on rear
• >30 M z bandwidth
• Front panel monitoring output
• Cable equalisation to 300 metres
• Various clamping options
• Longitudinal hum stripping
• Front panel EQ & gain adjustment
BLOCK DIAGRAM VA-700 SIGNAL PAT
CABLE
EQUALISATION
& HUM
REJECTION
VDA
+ DC OFFSET
O/P 1
O/P 2
O/P 3
O/P 4
O/P 5
O/P 6
O/P 7
O/P 8
O/P 9
O/P 10
MON O/P
ANALOGUE
VIDEO I/P
CLAMPING
CCT

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 6 of 23 Revision 10
TEC NICAL SPECIFICATIONS
Input:
Type Differential AC coupled.
Number 2.
Impedance Looping.
Return loss > 46 dB to 6 MHz.
um rejection > 40 dB.
Maximum level > 2 Vp-p (0 dB gain).
Outputs:
Type DC coupled.
Number 11 (Ten on rear and one on front panel).
Impedance 75 Ω source terminated.
Return loss > 40 dB to 6 MHz.
Overload 3.0 Vp-p on 4.43 MHz sine wave;
2.5 Vp-p on pulse.
DC level Adjusta le to 0 V.
Performance:
Gain ± 3 dB. Adjusta le from front panel.
Frequency response ± 0.1 dB from 20 Hz to 20 MHz;
± 0.2 dB from 20 Hz to 30 MHz.
Differential gain < 0.1% at 4.43 MHz (12.5% - 87.5% APL).
Differential phase < 0.1° at 4.43 MHz (12.5% - 87.5% APL).
Noise < -70 dB (unweighted).
Cross talk < -75 dB ( etween modules).
Transit time < 22° at 4.43 MHz.
Cable Equalisation Up to 300 m, for Beldin YR23769 ca le.
Power requirement:
Voltage 28 Vac CT (14-0-14) or ±16 Vdc.
Power consumption < 3.5VA (all outputs loaded in 75 Ω).
Other:
Temperature 0 - 50°C am ient.
Mechanical Suita le for mounting in IRT 19" rack chassis with input, output and power
connections on the rear panel.
Finish Front panel Grey ackground, lack lettering & red IRT logo.
Rear assembly Detacha le silk-screened PCB with direct mount connectors to Eurocard and
external signals.
Dimensions 6 HP x 3 U x 220 mm IRT Eurocard.
Due to our policy of continuing development, these specifications are su ject to change without notice.

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 7 of 23 Revision 10
CONFIGURATION
The VA-700 may e configured for several modes of operation. This is achieved y various link settings as outlined
elow.
The VA-700 is normally delivered set for internal clamp operation and no su -modules fitted.
1. No su -module LK 2 - LK 3 soldered on oard.
LK 6 - LK 7 soldered on oard.
2. Su -module: See instructions for each module (O solete – no longer availa le. Reference for
previous modules sold already in existence).
Cable compensation:
Circuitry provides compensation for up to 300 metres of Beldin YR23769 ca le, links 8a and 8 are used to provide
ranging of the compensation.
A short on link 8a will allow for ca le lengths of 75 m - 300 m to e compensated.
Moving the link to position 8 will allow for ca le lengths of 0 - 75 m to e compensated.
Clamping option:
Decide if the clamp feature of the VA-700 is required. In general the clamp feature is useful if the video signal is
always composite.
If you are using the VA-700 to distri ute pulses or su -carrier the clamp feature should e disa led (LK 1 installed),
otherwise LK 1 should e removed.
External clamp reference:
An external video signal can e used to provide the reference for the clamp pulse generator circuit in the VA-700.
The signal path from outputs 9 and/or 10 can e wired to the input of the clamp reference uffer amplifier.
On the VDA remove the link etween LK 10 - LK 12,
and complete links LK 12 - LK 13, LK 14 - LK 15 and LK 16 - LK 17.
Remove R 70 and R 71 connect a wire link etween the rear pads of the R 70 position, the R 71 position and
the rear pad of the unused R 80 position.
The external clamp reference can now e looped through from the connector 9 and 10 positions on the rear
assem ly.
Alternately:
A terminated input for the external clamp reference can e provided y using only the output 10 connector
position.
On the VDA remove the link etween LK 10 - LK 12,
and complete links LK 12 - LK 13, LK 14 - LK 15 and LK 16 - LK 17.
Remove R 71 and insert in the R 80 position.
Now wire the end pads of R 80 and the R 71 position together.
This will give a terminated input for the external clamp reference from output connector 10 on the rear
assem ly.

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 8 of 23 Revision 10
RGB video distribution:
When operating three VDA's in a group for RGB signal distri ution only the green signal will carry sync information.
The video signal from the input amplifier of the GREEN signal VDA can e sourced to the other VDA's y
rewiring links on the 'plug-in area' of the VDA's.
By rewiring the signal path to VDA outputs 9 and 10 these connectors can e used to carry the GREEN video
signal to the RED and BLUE VDA's clamp pulse generator circuitry.
On the GREEN VDA complete links LK 11 - LK 13, LK 14 - LK 15 and LK 16- LK 17.
Remove R 71 and connect a wire link etween the rear pad of the R 71 position and the rear pad of the
unused R 80 position.
This will source the video to output connector 10 on the rear assem ly.
On the RED and BLUE VDA's remove the link etween LK 10 - LK 12,
and complete links LK 12 - LK 13, LK 14 - LK 15 and LK 16 - LK 17.
Remove R 70 and R 71 connect a wire link etween the rear pads of the R 70 position, the R 71 position and
the rear pad of the R 80 position.
The external clamp reference from the GREEN VDA can e looped through from output connector 10 on the
GREEN VDA to output connectors 9 and 10 on the RED and BLUE VDA rear assem lies.
Alternately if all 10 video outputs are required the remote connector on the rear assem lies can e used to loop
the clamp reference video from the GREEN VDA to the RED and BLUE VDA's.
On the GREEN VDA complete links LK 11 - LK 13, LK 14 - LK 15 and LK 16 - LK 17.
This will source the video to the remote connector on the RB-601 rear assem ly.
C 1 = ground, C 2 = signal and C 3 = ground.
On the RED and BLUE VDA's remove link etween LK 10 - LK 12,
and complete links LK 12 - LK 13, LK 14 - LK 15 and LK 16 - LK 17.
The external clamp reference from the GREEN VDA can now e looped through via the remote connectors
on the three VDA rear assem lies.
Location of links & user settings:
F
R
O
N
T
P
A
N
E
L
Sub-module area
(No Longer Available)
RV 1 Gain
RV 2 EQ
LK 6 LK 7
LK 1
Rear
Assem ly
PCB 802756
PC Board Layout
Relative Position of User Settings
(Not to scale)
R 70
RV 5
LK 2 LK 5
LK 3 LK 4 LK 11 LK 13 LK 10 LK 12
LK 15 LK 17
LK 14 LK 16
R 80
R 71
RV 4
LK 8
RV 3

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 9 of 23 Revision 10
INSTALLATION
Pre-installation:
andling:
This equipment may contain or e connected to static sensitive devices and proper static free handling precautions
should e o served.
Where individual circuit cards are stored, they should e placed in antistatic ags. Proper antistatic procedures
should e followed when inserting or removing cards from these ags.
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 the correct polarity is o served and that DC supply voltage is maintained within
the operating range specified.
Earthing:
The earth path is dependent on the type of frame selected. In every case particular care should e taken to ensure
that the frame is connected to earth for safety reasons. See frame manual for details.
Signal earth: For safety reasons a connection is made etween signal earth and chassis earth.
No attempt should e made to reak this connection.
Installation in frame or chassis:
See details in separate manual for selected frame type.
Video connections:
Connect the video input to one of the two input connectors, and if the input is not to e looped, terminate the
other input with a 75 Ohm termination plug.
If you require the hum stripping feature to work remem er that the input ca le sheath must not e connected to
ground except at its source. Connect outputs as required.
Connect as many outputs as required. Each video output must e connected to a 75 Ω terminated load for proper
output level.

VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 10 of 23 Revision 10
Front & rear panel connector diagrams
O/P 1
O/P 3
LOOPED I/P
O/P 9
O/P 5
O/P 7
O/P 2
O/P 4
I/P
O/P 10
O/P 6
O/P 8

DL-700 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 11 of 23 Revision 10
DELAY & FILTER AMPLIFIER SUB-MODULE
(NOTE: Obsolete – No Longer Available. Information for existing modules only)
GENERAL DESCRIPTION
The DL-700 delay and filter mounting amplifier su -module allows two DIL delay lines or filters to e fitted to the
VA-700 Eurocard video distri ution amplifier for correction of signal timing or shaping of the amplifier frequency
response.
In addition to allowing fitting of fixed or varia le delays the DL-700 provides an optional amplifier with up to 3 dB
of gain to compensate for losses in delay lines without affecting the gain range of the VA-700 itself.
A delay trim adjustment of ±3 ns is provided which may e included in the signal path if required. When installed in
the IRT Eurocard VDA type VA-700 this trim control is aligned with a hole in the front panel to allow fine
adjustment of the delay when in operating configuration.
The DL-700 provides two sockets for fitting DIL delay lines or filters; one of up to 40 pins and one of up to 48 pins.
Pins normally used for grounding connections are connected to ground directly whereas pins normally used for
inputs and outputs are connected to pads to allow the user to easily configure the oard to the selected delay or
filter configuration required.
Although delay lines typically produce a low pass filter effect, an additional filter may e included for antialiasing or
to provide a step or “ rickwall” effect. Filters may e fitted to provide gaussian, antialiasing, step, emphasis, de-
emphasis or special equalisation characteristics.
Standard features:
• Usea le with most common rands of DIL delay lines and filters.
• Accommodates one or two delay lines or filters.
• 3 dB gain availa le.
• ±3 ns trim accessi le through front panel of VA-700 VDA.
Equipment provided:
Standard: DL-700 Delay or filter amplifier su -module.
Optional: DIL delay lines or filters.
A list of filters and delay lines availa le from IRT may e o tained
y contacting your IRT sales representative.

DL-700 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 12 of 23 Revision 10
TEC NICAL SPECIFICATIONS
Overall performance:
Overall performance is determined y the choice of delay lines or filters fitted, and choice of amplifier gain and
delay trim. Suita ility to any particular application should therefore e determined y experiment.
Amplifier only:
Input:
Type DC coupled.
Impedance 75 Ω.
Maximum Level > 2 V p-p (0 dB gain).
Output:
Type DC coupled.
Impedance 75 Ω source terminated.
Gain: +3 dB. Adjusta le y fitting programming resistor.
Power requirements :
Voltage ± 12 Vdc from VA-700.
Power consumption 50 mA (additional to VA-700).
Other:
Temperature range 0 - 50° C am ient
Mechanical Suita le for mounting in IRT VA-700 VDA.
Dimensions 135 x 42 mm PCB.
Optional accessories Instruction manual
Filter or delay modules.
Due to our policy of continuing development, these specifications are subject to change without notice.

DL-700 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 13 of 23 Revision 10
CONFIGURATION
The DL-700 is delivered with a jumper from the input to output DIL pads, the amplifier set for 0 dB gain and the
delay trim connected.
Delay lines:
Consult data sheet for selected delay line to o tain pin-out information.
On the DL-700 plug-in module fit delay line(s) with pin 1 to the left for each position.
Wire in delay sections as required starting at the I/P pad and finishing at the O/P pad, using pads connected to the
delay line section(s).
Amplifier:
Select programming resistor R 3 to set gain of amplifier according to the following ta le:
Gain R 3 value
0.0 dB Omitted
1.0 dB 1,400 Ω
1.5 dB 887 Ω
2.0 dB 649 Ω
2.5 dB 499 Ω
3.0 dB 402 Ω
Fine adjustment to the gain should e made using the gain trim control on the supporting VDA.
Variable delay:
To configure the varia le delay section, use the link pads located near SK 2.
Enable:
Connect LK 1 - LK 2 and LK 3 - LK 4.
Disable:
Connect LK 2- LK 3 and cut links LK 1 - LK 2 and LK 3 - LK 4.
INSTALLATION
VA-700:
On the VA-700 in the plug-in area the following links changes must e made. Remove the link from LK 2 - LK 3, add
links from LK 3- LK 4 and leave the existing link etween LK 6 - LK 7.
DL-700:
Ensure that DL 700 is correctly configured as detailed in configuration section.
Carefully position the su oard over the VA-700 ensuring that all pins of PL 2 & PL 3 of the VA-700 slide neatly into
the corresponding socket positions of SK 2 & SK 3 of the DL-700.
Press down firmly and evenly on the DL-700 su oard ensuring that the cut-out in the top left hand corner just
clears the gain potentiometer on the VA-700 as the oard slides into place.
Check alignment of the delay trim adjustment capacitor with the hole provided in the front panel of the VA-700
and adjust oard position slightly if required.

AVD-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 14 of 23 Revision 10
VIDEO SYNC FAILURE DETECTOR SUB-MODULE
(NOTE: Obsolete – No Longer Available. Information for existing modules only)
GENERAL DESCRIPTION
The AVD-3120 video detector is designed to e used to indicate the presence of a video signal y detecting the
vertical sync component of a composite video signal. The detection circuitry used ensures that noise alone will not
trigger the detector.
The AVD-3120 video sync failure detector su -module may e fitted to the VA-700 Eurocard video distri ution
amplifier for indicating loss of incoming video signals to the VDA. An LED is fitted to the su -module, which extends
through the front panel of the VA-700 and a relay closure alarm output is availa le on the VA-700 rear connection
assem ly at the three pin remote connector.
The AVD-3120 has an internal threshold adjustment, which is factory set to cover the majority of applications, ut
is accessi le to the user for special applications.
Note that all references to the VA-700 are also applica le to the VA-700T except where noted to the contrary.
Standard features:
• Front panel LED failure indication.
• Changeover relay alarm contacts.
• Adjusta le threshold.
Equipment provided:
Standard: AVD-3120 Delay or filter amplifier su -module.
3 pin IDC connector for remote alarm.

AVD-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 15 of 23 Revision 10
TEC NICAL SPECIFICATIONS
Video:
Video system Composite PAL or NTSC.
Video input level 0.7 to 1 Volt p-p composite video.
Input impedance High impedance ridging.
Performance:
Detection threshold - 6 dB referenced to 1 Vp-p composite video signal (factory setting).
Internal preset adjustment effective in the range 0.4 to 0.7 Volts p-p
composite video.
Response time:
Alarm active 12 ms after sync loss.
Alarm reset 800 ms after sync return.
Indicators & alarms:
Visual indicators VIDEO FAIL ALARM LED.
Alarm output Relay circuits operated from alarm logic.
Changeover relay contact set.
Relay contact rating 24 Vdc - 1 A;
100 Vac - 0.3 A.
Alarm connector 3 pin 0.1 inch spaced socket strip with mating locking plug assem ly
mounted on rear assem ly of VA-700.
Power requirements :
Voltage ± 12 Vdc from VA-700.
Power consumption 50 mA (additional to VA-700).
Other:
Temperature range 0 - 50° C am ient.
Mechanical Suita le for mounting in IRT VA-700 VDA.
Dimensions 135 x 42 mm PCB.
Due to our policy of continuing development, these specifications are subject to change without notice.

AVD-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 16 of 23 Revision 10
CONFIGURATION
The AVD-3120 requires no configuration or adjustment for normal applications.
Detector threshold:
The detector threshold is set y RV 1 and is factory adjusted to respond to a 6 dB loss in signal level referenced to a
1 volt p-p composite video signal at the input to the VA-700 VDA with the looping connector terminated y
75 Ohms.
Adjustment of RV 1 can change the threshold level y approximately ±3 dB.
To adjust the threshold level:
1. Apply a 1 volt p-p video signal to the VDA rear assem ly with the VDA operated on the ench from a
14 - 0 - 14 Volts AC supply or on an extender oard in the Eurocard frame. Ensure that the VDA input
is correctly terminated in 75 Ω.
2. Reduce the input level to the trip level y attenuating the input.
3. Adjust RV 1 so that the LED status indicator on the front panel just changes state.
INSTALLATION
VA-700:
The following links should e in place:
LK 2 - LK 3,
LK 6 - LK 7.
Under normal circumstances no adjustments need to e made to the VDA in order to fit the AVD-3120 and the
performance of the VDA will not e affected y the inclusion of the AVD-3120.
AVD-3120:
If a second equaliser su -module is fitted to the VA-700 as is the case with the VA-700T this may first e unplugged
from its socket, taking note of the correct alignment so as to facilitate replacement after the AVD-3120 is fitted.
This step is not essential, ut will make insertion of the AVD-3120 easier.
Carefully position the su oard over the VA-700, tilting to place the LED indicator in line with the ”TRIM” hole in
the front panel. Ensure that all pins of PL 2 & PL 3 of the VA-700 slide neatly into the corresponding socket
positions of SK 2 & SK 3 of the AVD-3120.
Press down firmly and evenly on the AVD-3120 su oard ensuring that the cut-out in the top left hand corner just
clears the gain potentiometer on the VA-700 as the oard slides into place.
Check alignment of the sync alarm LED with the hole provided in the front panel of the VA-700 and adjust LED
position slightly if required.
If second equaliser su - oard was removed from VA-700, re-insert it carefully ensuring that all pins are correctly
aligned with the socket.
Connect alarm wiring to remote connection on rear assem ly using the three pin IDC socket provided.

CVA-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 17 of 23 Revision 10
REMOTE GAIN CONTROL SUB-MODULE
(NOTE: Obsolete – No Longer Available. Information for existing modules only)
GENERAL DESCRIPTION
The CVA-3120 is a video gain su -module designed to e fitted to the IRT VA-700 general purpose video
distri ution amplifier to provide remote access to the gain of the VDA.
The control signal is completely separate to the video path and so does not cause noise in the video path. The
control signal is damped to prevent noise on the external control causing short term gain variations.
Control may e y either a DC control signal or via a simple potentiometer connected to the VDA. This makes the
control suita le for oth direct manual use or for operation at remote locations using other methods to generate
the required DC control voltage.
The high performance of the su - oard results in no significant degradation in the performance of the VDA.
Standard Features:
• Fits standard VA-700 Eurocard VDA.
• Gain range ±3 dB.
• Noise free remote control via DC level.
• Control y potentiometer or DC input.
Applications:
Centralised control for fast set-up of levels in:
• O.B. vans.
• Master control.
• Camera gain matching.
CVA-3120 Sub-module
DC gain
controlled
amplifier
2
3
1
+12 Vdc
1 KOhm 0 to + 12 Vdc
Buffer amplifier
Input from
VA-700
VDA
input
stage
Output to
VA-700
VDA
output
stage

CVA-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 18 of 23 Revision 10
TEC NICAL SPECIFICATIONS
Video:
Video system Composite PAL or NTSC.
Performance:
Performance figures given are for overall performance when the su -module is mounted in a VA-700 VDA.
Gain range ± 3 dB.
Differential phase < 0.1° (at 3.5 to 4.3 MHz).
Differential gain < 0.05% (at 3.5 to 4.3 MHz).
Signal to noise ratio < -70 dB.
For other performance specifications see VA-700 data sheet.
External control: Potentiometer 1 kW connected to pins 1, 2 & 3 of 3 pin remote control
connector on rear panel of VA-700.
DC 0 - 12 Vdc connected to pin 3 of 3 pin remote control
connector (pin 1 Gnd) on rear panel of VA-700.
Response time constant < 0.1 seconds.
Power Requirements:
Voltage ± 12 Vdc taken from VA-700.
Power consumption <3 0 mA additional to VDA requirement.
Other:
Temperature range 0 - 50° C am ient
Mechanical Suita le for mounting in IRT VA-700 VDA in designated
su - oard area. Note that only one su - oard may e fitted at
one time.
Dimensions 124 mm x 41 mm PCB
Standard accessories (supplied with su -module) Matching 3 pin IDC connector for remote control connector on
rear of VDA.
Part # 1300-103-426.
Due to our policy of continuing development, these specifications are subject to change without notice.

CVA-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 19 of 23 Revision 10
CONFIGURATION
The CVA-3120 requires no configuration or adjustment for normal applications other than as detailed in the
installation procedure.
Response time:
If the damped response time is unsuita le for the proposed application the value of C6 may e changed
accordingly, ut should not e omitted altogether. The chosen value of 10 µF gives a time constant of
approximately 0.1 seconds which is considered a good compromise for normal roadcast use.
Maximum gain:
The 6 dB amplifier U2 may e adjusted to greater or lesser gain settings if required although this should rarely e
necessary. The com ined gain and EQ circuits of the VA-700 and the CVA-3120 should e sufficient to compensate
for any losses in normal circuits.
The maximum gain is set y resistors R6 and R7 and the gain is determined y the equation:
V
O
= [(R
7
+ R
6
)/R
6
] * V
IN
Where V
O
is the output voltage; and V
IN
is the video input signal.
Maximum attenuation:
If greater attenuation is required the value of R 2 may e adjusted to provide the necessary gain range. Please note
however that some performance specifications may not e met if the gain range is greatly extended.
External DC control:
The attenuator network on the control input is adjusted for use with a 0 to 12 Vdc control signal and exhi its a
dead and at the maximum gain position (0 Vdc) to ensure that this can e achieved.
If control voltage ranges other than 0 to 12 Vdc are required to e used then the resistor values of R 2 & R 3 may
e adjusted to provide the correct division ratio for the input voltage range so that the voltage at pin 3 of U 1
varies etween 0 and 0.5 Vdc for a 6 dB adjustment range.
Care should e taken to ensure that R 2 is kept to a sufficiently high value to offer protection to the IC input and C
6 should e adjusted to provide a suita le damping factor for noise which may e induced into the control line.
For more information on using this input please consult the Gennum data sheet for the GT4123.

CVA-3120 VA-700
I.R. T. Communications Pty L t d | www .i rtcommunications . c o m
Page 20 of 23 Revision 10
INSTALLATION
VA-700:
The following links should e in place: LK 2 - LK 3,
LK 4 - LK 5
and the following link should e removed: LK 6 - LK 7.
CVA-3120:
If a second equaliser su -module is fitted to the VA-700 as is the case with the VA-700T this may first e unplugged
from its socket taking note of the correct alignment so as to facilitate replacement after the CVA-3120 is fitted. This
step is not essential, ut will make insertion of the CVA-3120 easier.
Carefully position the su oard over the VA-700. Ensure that all pins of PL 2 & PL 3 of the VA-700 slide neatly into
the corresponding socket positions of SK 2 & SK 3 of the CVA-3120.
Press down firmly and evenly on the CVA-3120 su oard ensuring that the cut-out in the top left hand corner just
clears the gain potentiometer on the VA-700 as the oard slides into place.
If second equaliser su - oard was removed from VA-700, re-insert it carefully ensuring that all pins are correctly
aligned with the socket.
Connect remote wiring to remote connection on rear assem ly using the three pin IDC socket provided.
The remote gain control potentiometer should e wired as follows:
Gain adjustment:
Under normal circumstances no adjustments need to e made to the VDA in order to fit the CVA-3120.
Under normal operating conditions using a 1 kΩ potentiometer as the control device the normal operating
position for the potentiometer should e at approximately half setting. If it is desired to cali rate this position then
the central position should e set and marked and the front panel gain of the VA-700 adjusted until a 1:1 gain is
achieved through the VDA.
The remote gain control may now e varied and the resultant gain settings marked against the potentiometer
position.
If the CVA-3120 is fitted to the VDA and no external connection is made to the remote gain input control then this
control will default to the minimum attenuation setting and so the output of the VDA will e increased y
approximately 3 dB.
If the CVA-3120 is required to function only as an attenuator then the VDA gain should e adjusted for a 1:1 gain
when the CVA-3120 control input is at 0 Vdc. The CVA-3120 will now give 0 to 6 dB of attenuation from the 1:1
setting.
2 +12 Vdc
3 Control output
1 Gnd
Maximum attenuation
Maximum gain