1 March, 2005
V1629OM.DOC/ A
Page 9 of 10
3.8 ADJUSTMENTS
Both the V1627 and V1628 have internal adjustable potentiometers for setting up gains and black
levels. They are shown in this table:
POT. BUILD OUTPUT
PARAMETER
VR 1
Both
A on CVBS
CVBS Gain
VR 2
Both
A on CVBS
CVBS Black
VR 3
Both
A on Y/C
Y Black
VR 4
V1628 Only
C on YUV
Sync Amplitude
VR 5
V1628 Only
C on YUV
Y Amplitude
VR 6
V1628 Only
C on YUV
Y Black Level offset
VR 7
V1628 Only
D on YUV
Pr Zero Offset
VR 8
V1628 Only
E on YUV
Pb Zero Offset
3.9 SIGNAL
FAIL
If the input signal to either channel fails, then the SDI input stages recognise the absence of the
270MHz, and mutes the output. Since the coder stage thus loses its clock there will be no output.
All analogue outputs are switched off to a dc level. For the Coder outputs, this is in the region of the
sync tips, approximately -300mV. For the YC outputs, if selected, the dc voltage is near blanking
level. There is no facility to generate a colour black signal.
If the input signal to a channel has failed, then PLUGE is not available on that channel.
3.10 GPI
The GPI input is for selecting PLUGE onto the outputs. It is active when the unit is in either LOCAL
or REMOTE mode and will always put the outputs of both channels to PLUGE unless one or other
of the relevant internal DIL switches is set to inhibit it.
The GPI is connected through a BNC connector. The ‘active’ contact has an internal pull-up resistor
(6K8) to +5V. The external control device should connect this to Ground, i.e. the screen of the BNC.
Note that this means that a 75R termination is enough to enable PLUGE.
