Video Processing Circuit; Camera Detection Circuit; Camera Selection Circuit; Signal Processing Circuit - Panasonic WV-BM90 Service Manual

2-2 Video Processing Circuit

2-2-l Camera Detection Circuit
This circuit detects whether camera is connected or not. This
monitor has four camera detection circuits and these four
circuits are exactly same, so that the camera detection crrcurt
for camera-l will be described.
When the camera WV-BL90 is connected to camera-l I N
connector CNlOl and power switch of the vrdeo monitor is
turned ON, approx. + 12V DC is supplied from the camera
power circuit to the connected camera. At this time, + 12V
DC is also supplied to 44 for turning
level at collector of Q5 is supplied to pin 7 of IC6 and lC6
recognizes that camera-l is connected.
When camera is not connected to the video monitor or the
cable is disconnected in the operating condition, no
coaxial
DC power is supplied to power line since misconnection
protection circuit functions. At this trme, both Q4 and Q5 are
turned ON, pin 7 of lC6 becomes L level and IC6 recognizes
that camera-l is not connected.

2-2-2 Camera Selection Circuit

This circuit selects the camera signal which is supplied to
signal processing circuit for observing the selected prcture on
the monitor. Four camera selection circutts are existed on the
monitor and are exactly same, so that the camera-l will be
described.
When camera-l is selected by sequence mode or spot
monitoring mode, pin 2 of IC6 becomes L level and the L level
is fed to Q6 to turn ON Q6. Therefore the camera-l signal
obtained at Pin 3 of 46 is supplied to signal processing circuit.

2-2-3 Signal Processing Circuit

The video signal from the camera-l supplied to Q6 on the
control board is mixed with the VD pulse which is sent
through VD pulse generator Q12/Q13 and inverter 45 and
supplied to the camera for vertical synchronization.
The vrdeo srgnal with VD pulse is supplied through 96 to
clamp circuit Q20.
In the clamp circuit, horizontal (H) and vertical (V) blanking
periods of video signal is clamped by the clamp pulse which is
generated by sync separator Q19 and clamp pulse generator
consisting of ICl (a) - (d).
The video signal is sent to VD erase circuit Q21 where the
This signal is supplied to slicer consisting of Q22 - 424 where
low level of sync signal is clipped and the sync level is set to
The video INT/EXT switching circurt consisting of 426 - Q29
selects either composite video signal entering VIDEO INPUT
connector or camera video signal swrtched by microprocessor
OFF and Q5 OFF. The H
IC6. When the input selection switch 5~3 on the VR board is
set to CAMERA posltlon, pin 53 of IC6 sends low level to 427
a n d Q29 for turning ON 427 and t u r n i n g O F F Q2R.
Therefore camera video signal is selected and supplied to
Main board. When SW3 is set to EXT position, high level is
sent to 427 and Q28 and composite video signal externally
enters to the video monitor is supplied to Main board.
The video output circuit consisting of 430 - 431 amplifies
the camera video signal for setting it to specified signal level
and compensates the frequency response. This signal is
supplied to VIDEO OUTPUT connector.
2-3 Remote Control Circuit
This circuit supplies the camera selection signal and reset
signal to the remote control unit WV-32 for auto panning
head or another video monitor for remote control.
This circuit
also
connected buzzer or chime.
When the camera-l is selected by sequence control for
example, pin 2 of microprocessor IC6 becomes low (L) level
during the sequence time set by VR9 (TIME ADJ) on the
Volume board. This signal supplied through C64 and RI 16
IS
to 454 and both 454 and 455 are turned ON at the decay
timing of signal and negative trigger obtained at collector
On the other hand, when the camera-l is selected by spot
monitor control for example, pin 2 of IC6 becomes L level
during camera-l button is depressed and the L level is
supplied to Q54 for turning both 454 and 455 ON and
negative trigger obtained at collector Q55 is also supplied to
connected unit for selecting camera-l.
The remote output circuit for the camera-2, camera-3 and
camera-4 functions as same manner as camera-l remote
output circuit.
Remote Reset Output Circuit
l
When sequence button is depressed while the video monrtor
is operated at spot monitor mode, pin 22 of IC6 becomes L
level during the button is depressed. This signal is supplred to
signal/pulse obtained at collector 463 is supplied to
connected products through reset terminal.
Alarm Standby Output Circuit
l
While the video monitor is operated at standby mode and
spot monitor control signal
IS
terminal, pin 54 of IC6 becomes L level. This is sent to Q51 to
turn both 451 and QSO ON and the negative signal/pulse
obtained at collector Q50 is supplied through standby alarm
output teimin'al to connected buzzer or chime to ring it.
At this time, correspond camera signal is selected and
observed on the monitor screen.
fed to the spot monitor control
. . ._