Lectrosonics VS1 - Manual (Page 3)

THEORY OF OPERATION
The general operation of the VS1 will be described in this section, while the specifics of each programmable option
will be outlined in the Operating Instructions.
A Motorola MC68HC705 microcontroller is the heart of the VS1. The MC68HC705 controls both the switching
relationships between the logic inputs and logic outputs, as well as all user interface functions. Since the
MC68HC705 is so highly integrated, parts count is kept to a minimum in the VS1, resulting in higher reliability.
The VS1 provides intelligent connection of an automatic mixer to a video switcher by interpreting the microphone
activity and keying the appropriate camera. A programmable Input Time Delay allows a user selectable waiting
period after microphone activity commences before the camera associated with that microphone is activated. This
prevents unwanted camera switching caused by coughs, paper rustling, and other transient non-speech sounds. A
programmable Hold Time Delay allows a user selectable waiting period when microphone activity stops before
moving to another camera. This hold time is used to cover pauses in speech, again avoiding unwanted camera
switching. When no microphones are active, the VS1 may be programmed either to hold the last active camera or
switch to an overview camera. When multiple microphones are simultaneously active, the VS1 may be
programmed to rotate between all active microphones, switch to the overview channel, or key two cameras (for
video switchers with split screen capability).
Figure 1 - VS1 Block Diagram
An override capability is provided if one or more outputs need to take precedence over other outputs. Any
output(s) may be set as an override output. When an override output becomes active, no other outputs are allowed
to become active until the override output is no longer active. Override capability is useful if a camera needs to be
forced on, irrespective of microphone activity. A switch may be connected to the logic input of an override output to
provide a means to "force on" that output.
Besides the normal mode of operation, two other operational modes are provided on the VS1: Scan mode and
Manual mode. The Scan mode continuously rotates through all eight outputs, activating them each individually.
The Manual mode allows any or all outputs to be activated or deactivated manually from the front panel.
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