Burst Electronics VS4x1(R) - Manual (Page 3)

1 VS4x1 & VS8x1 Video Switch
Introduction
Congratulations on your purchase of VS4x1/VS8x1 Vertical
Interval Switcher. This manual will explain the various
functions of the VS4x1/VS8x1 (as well as the RS232
options, model VS4x1R/VS8x1R). Unless otherwise stated,
all functions of the VS4x1 are the same for the VS8x1.
Overview
The model VS4x1 is a four (4) input active switcher (VS8x1
is an eight (8) channel active switcher). The appropriate
front panel channel switch selects the output. An LED
indicates the currently selected active channel. Switching
from one video source to another is done during the
vertical interval. Both products use digital logic that inhibits
the selection of an inactive input (no video). This is a safety
feature that can be disabled, explained later. The logic
detects sync to determine if video is present.
Operation
When a channel is selected, the switcher waits for the start
of the next vertical interval to change to the selected input.
If the inputs are synchronous (genlocked), this will allow a
seamless transition from one input to another. All inputs are
DC clamped, at the back porch (color burst), to ground by
the video switcher. The output is also ground referenced. If
there are any level shifts on the incoming video, the video
switcher will eliminate these offsets and ground reference
the outgoing video.
Input Termination
Each channel input has a 75 Ohm termination resistor. This
termination may be removed, resulting in the video
switcher being in the bridging or HiZ mode. This allows
looping of the inputs (looping adapter part number BNC-
Four/Eight Input Switcher