Ovation Systems Gemini 2 User manual

Issue 1.1 Ovation Systems Ltd. Page 1
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Gemini-4 User Guide
Video Link Expander
Gemini 2 & 4
Video Link Expander
User Guide
Ovation Systems Ltd.
Great Haseley Trading Estate
Great Haseley
Oxfordshire
OX44 7PF
UK
Tel: [phone]
Fax: [phone]
Email: [email protected]
Web: www.ovation.co.uk

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Gemini-4 User Guide
Video Link Expander
1 Introduction
Gemini-4 allows extra cameras to be easily sent over an existing video surveillance link
without the need of any modification. Gemini operates by multiplexing up to 4 video inputs
together into one video stream suitable for transmission over a coax, fibre-optic or RF/
microwave link. At the receive site, the Gemini decoder splits the multiplexed stream back
into separate outputs ready to be viewed on individual monitors, or a combination of scaled
pictures on one monitor, as required. See Figure 1: Gemini Application Diagram.
Gemini
Decoder
Gemini
Encoder
Camera 1
Camera 2
Camera 3
Camera 4
TV
1
TV
3
TV
2
TV
4
Any real-time
video link
- Coax
- Fibreoptic
- RF
Figure 1: Gemini Application Diagram.
Gemini provides the fastest possible picture update rates by using video field multiplexing.
The picture update rate per channel is dependant upon the number of active inputs to the
encoder and the video standard used. Please refer to Table 1 below showing details of
Gemini’s update rates:
Number
of
Inputs
PAL Picture Update
Rate
(Pictures per Second)
NTSC Picture Update
Rate
(Pictures per Second)
1 50 60
2 25 / 25 30 / 30
3 25 / 12.5 / 12.5 30 / 15 / 15
4 12.5 / 12.5 / 12.5 / 12.5 15 / 15 / 15 / 15
Table 1: Gemini Picture Update Rates

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Gemini-4 User Guide
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2 Quick Start Guide
The Gemini system is supplied as an encoder / decoder pair with DC power leads. The
following describes the basic installation:
2.1 Ensure the units are configured for the correct video standard (PAL or NTSC). A “PAL”
or “NTSC” label on the side of the unit indicates the configuration.
2.2 Ensure the encoder’s and decoder’s mode control switches are both set to “0” as
shown in Figure 2.
2.3 Connect 7 to 32 V DC power source to the encoder and decoder to units using Lemo
cable assembly provided, as shown in Figure 2. As a guide the encoder requires
approximately 300 mA, the decoder 400 mA, at 12 Volts DC.
Red
+ 6 to
32 V
DC
Blue
0 V
Video
Expansion port
& RS232 Mode
Control
Switch
DC Power
0
1
9
2
A
3
B
4
C
5
D
6
E
7
F
8
Figure 2: Gemini Interfaces / User Control
2.4 Connect up to 4 video sources (cameras) to the encoder’s video inputs. Any
combination of input channels may be used. All video connections are nominally 1 V pp
with 75Ωterminations.
2.5 Connect the encoder’s video output to the real-time video link (see Figure 1).
2.6 Connect the output of the video link to the decoder’s input (see Figure 1).
2.7 Connect the number of video monitors required to the Gemini decoder’s outputs (see
Figure 1).

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Gemini-4 User Guide
Video Link Expander
3 LED Indicator.
The bicolour LED indicator located on the side of the unit shows the status of the Gemini
system with the following functionality:
LED
Function
Encoder
Function
Decoder
Function
Static red Unit has failed self
test
Unit has failed self test
Static Green N/A Video OK but not
Gemini Encoded
Flashing red No valid video inputs No valid video inputs
Flashing
green /
Red*
Gemini multiplexing
OK
Gemini demultiplexing
OK
Table 2: LED Indicator Functions
*The LED indicates the status of the video inputs to the Gemini encoder. In normal operation
(mode 0) the LED will flash 4 times followed by a gap of approximately 2 seconds. The first
flash indicates the status of input 1 (green for OK, red for no valid input) and the second flash
the status of the second input and so on. For example, if video was connected to encoder
inputs 1,2 & 4 then the LED flash sequence is as follows:
Green….Green …. Red …. Green ….{2 second pause}... Green….Green …. Red …. Green.
1 2 3 4 1 2 3 4
If the system is connected and working correctly then the decoder’s LED will follow the same
sequence as the encoder.
If a manual (1, 2, 3 or 4 channel) mode is selected, then the LED will flash red / green the
corresponding number of times between the 2 second pause.
4 On-Screen Display
An on-screen display (OSD) is included on the output the encoder. As standard, this OSD
shows the input number of each field, in the form “Camera 1”, “Camera 2”, “Camera 3” or
“Camera 4”. In auto-mode the background colour beneath the OSD text changes to indicate
the number of active inputs. If there are no valid video inputs the OSD will show a “No
Master” error message.
5 Video By-pass
To aid fault finding, when the encoder is powered down, Input 1 is passed directly to the
Output using a “drop-out” relay. Similarly, the decoder Input is passed directly to the
decoder’s Output 1 when the DC power is not applied.

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Gemini-4 User Guide
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6 Decoder Picture-in-Picture Modes
The mode switch on the side of the unit selects the decoder’s picture-in-picture modes with
the following function:-
2- Bot ½ 4- Bot ½
1- Top½ 3- Top½
1-Left
½
3 -Left
½
2 -Right
½
4 -Right
½
1
1
1
4
2
2
2
1
3
3
3
3
2
4
4
4
3
3
3
3
1
1
1
1
11
11
4
4
4
4
2
2
2
2
2
2
2
2
33
4
4
3
3
0. Normal De-mux
mode
1. Switch Cameras
2. Switch Cameras
3. Switch Cameras
4. Side by side
without scaling
5. Side by side
with scaling
6. A above B
without scaling
7. A above B
with scaling
8. Two way PIP
mode 1
9. Two
mode 2
way PIP
A. Two
mode 3
way PIP
B. Two way PIP
mode 4
C. 3 way PIP
D. 4 way PIP
E. Quad
F. Full Picture cycle
Mode Output
1
Output
2
Output
3
Output
4
1>2>3>4 3>4>1>2
11 22
33 44
Table 3: Decoder Picture In picture modes.

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Gemini-4 User Guide
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7 Encoder Modes
In normal operation, mode 0, the encoder automatically configures itself to share the
available update rate over the number of cameras actually connected. However, there are a
number of manual modes that allow for a fixed number of cameras (which helps reduce
encoder power consumption) together with the possibility to allocate a priority update rate to
camera 1. Please refer to Table 4 below:
Mode
Switch
Position
Description Picture Rate Per Second
PAL (NTSC)
Input 1 Input 2 Input 3 Input 4
0 Auto
(Default)
Auto Auto Auto Auto
1 Cam 1 only 50 (60) - - -
2 Cam 1 & 2 only 25 (30) 25 (30) - -
3 Cam 1,2 & 3
only
25 (30) 12.5 (15) 12.5 (15) -
4 Cam 1,2,3,4 12.5 (15) 12.5 (15) 12.5 (15) 12.5 (15)
5 Cam 1
3 x Priority
25 (30) 8.5 (10.2) 8.5 (10.2) 8.5 (10.2)
6 Cam 1
9 x Priority
37.5 (45) 4 (4.8) 4 (4.8) 4 (4.8)
7 Do Not
Use
- - - - - - - -
8 Cam 1
47 x Priority
47 (56.4) 1 (1.2) 1 (1.2) 1 (1.2)
9 Cam 1
96 x Priority
48 (57.6) 0.5 (0.6) 0.5 (0.6) 0.5 (0.6)
A Do Not
Use
- - - - - - - -
Table 4: Gemini Encoder Update Rates Pictures Per Second for PAL Video
NTSC update rates are show in brackets.
In most applications it is expected that the Gemini encoder will be used in conjunction with a
corresponding decoder. However, there are applications where a single picture-in-picture
display of the inputs will suffice, and in this instance, the encoder may be configured to
operate stand-alone. The picture-in-picture modes are as follows:
Mode Description
B Input 1 with an insert of input 2
C Input 1 above input 2
D Input 1 beside input 2
E All 4 inputs, quad screen
F 2 second cycle through each input
Table 5: Encoder Picture In Picture modes
Note:The decoder is not compatible with the encoder’s picture-in-picture modes.

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Gemini-4 User Guide
Video Link Expander
8 Operation With Viewlock II Video Encryption System.
If a secured transmission link is required, it is possible to scramble the Gemini output using
Ovation Systems’ Viewlock II video encryption system as shown in Figure 3. It is not possible
to use a configuration where the video input to the Gemini encoder is scrambled.
Gemini
Decoder
Gemini
Encoder
Viewlock II
Encoder
Viewlock II
Decoder
Link
Video Inputs
Video Outputs
Scrambled
Video
Figure 3: Gemini and Viewlock II video scrambling configuration
Important: In PAL operation, the standard Viewlock II configuration is not interoperable with
the Gemini-2/4 system. This is caused by the two systems using the same video line to
transmit synchronising data. The solution is to change the Viewlock II’s data line by using the
VL2-Talk PC configuration software and serial programming cable.
For Gemini-4 users, the software and cable are available free of charge by contacting
Ovation Systems. Install the VL2-Talk software, as described in the accompanying user
guide, and then click the “Set For Gemini” button on the “Data Line” tab. Ensure this
procedure is repeated for all Viewlock II encoders / decoders.
NB: In NTSC operation, Viewlock II and Gemini-4 are compatible and do not require any
change to the standard configuration.
9 Operation with VCRs
It is possible to record the multiplexed output of the Gemini-4 encoder on a standard VCR
and decode the playback to 4 separate outputs using a Gemini-4 decoder. However, the
system will only operate with real-time recordings and is not compatible with any time-lapse
modes.
Note: Gemini-4 is unlikely to be compatible with any digital hard-disk video recorders due to
the compression and digitisation techniques employed removing the Gemini synchronisation
data.

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Gemini-4 User Guide
Video Link Expander
10 Trouble Shooting
If problems are encountered, initially check the system installation by the following
procedure:
10.1 Check that both Gemini units are set for the correct video standard (PAL or NTSC),
indicated by a small label on the side of the unit.
10.2 Check the DC supply to the Gemini units is within 7 to 32 Volts DC. The PSU’s should
have a smoothed output and be capable of providing at least 0.5 amps.
10.3 Whilst powered, set the encoder and decoder control switches to “0”. This will ensure
that both units are in a known and compatible state.
10.4 If practicable, connect the output of the encoder directly to the decoder’s input using a
BNC cable, to ensure the link is not causing the problem.
10.5 Check the encoder’s and decoder’s LED’s are flashing in the expected sequence for
the number of cameras connected to the encoder. See Section 3 on page 4 regarding
the LED function.
If problems persist, check for the following symptoms:
1. One or more output channels have intermittent or no colour.
This is usually caused by Gemini being unable to fully lock to the incoming video signal
due to off frequency video syncs or colour burst. This type of problem is often attributed
to camera set-up or performance. Please check the following:
a) For successful Gemini-4 operation it is vital that the master input (the lowest input
number to the encoder used) adheres strictly to the PAL or NTSC standard. Try
changing / swapping cameras into the encoder so a different camera is used as the
master channel.
b) Some cameras have the option external synchronisation which, if selected, causes
their syncs to be off frequency. This is function is often controlled by a camera DIP
switch marked “Int / Ext” which should be set for internal operation. For further
information, please refer to camera’s user guide.
2. The system operates OK with a direct BNC cable connection between the encoder
and decoder, but shows a “No Master” message when operated over a link.
This indicates the decoder is unable to lock-on to the incoming video. Probable causes
are incorrect video level (possibly double termination) or video sync distortion introduced
by the link. If available, check the video level and distortion to the input of the decoder
using an oscilloscope.