Studio Technologies 770 - Manual (Page 33)

Model 770 User Guide Issue 1, October 1997
Studio Technologies, Inc. Page 33
Model 770
All these “wordy” sentences are trying to
describe a simple procedure. Let’s take
our first example, where an “interrupt”
signal is coming from a control room in
New York. In most cases this signal would
need to be routed to the Model 770’s IFB
output; nothing should cause its level to
be muted or dimmed. If this is correct,
then this signal should be assigned as
interrupt. Assignment of another signal to
the interrupt bus, or activation of the front-
panel gooseneck microphone, will simply
cause these signals to be added
(summed) with the signal from New York.
The second example, audio from an off-air
receiver, is pretty straight forward; it
should be assigned as program. The third
example, the director cueing via a 2-way
radio, is simple too. It should be assigned
as an interrupt source.
Source Assignment Switches
Seven switches are provided to route the
source signals to the program and inter-
rupt audio buses. The sources are: mixer
section main and AUX audio, four IFB line
inputs, and telephone interface. The
switches have three mechanical positions;
left, center, and right which are labeled
respectively PGM (for program), OFF, and
INT (for interrupt). In the off position signal
is not connected to either of the buses. In
the program position signal is connected
to the program bus. In the interrupt posi-
tion signal is connected to interrupt audio
bus, as well as the interrupt signal detec-
tion circuit. There is absolutely no problem
assigning multiple sources to program or
interrupt.
Local IFB
The button labeled TALK TO IFB, located
on the lower-left-corner of the front panel,
is used to connect audio from the goose-
neck microphone to the interrupt bus, and
on to the IFB output. This allows cue or
setup information to be sent to the talent,
or other users of the IFB output. The
interrupt LED will light whenever the but-
ton is pressed, and the program audio will
be muted or attenuated (dimmed). If the
interrupt function is already active, the
gooseneck microphone audio will be
added (summed) with the other interrupt
signal. To prevent acoustic feedback,
pressing the talk to IFB button also causes
the IFB monitor output and the monitor
section’s monitor output to mute.
Interrupt LED
The yellow LED, labeled INTERRUPT, is
lit any time program audio is being inter-
rupted. There are two way an interrupt can
take place: by the presence of signal on
the interrupt bus, or by pressing the local
talk-to-IFB button.
Level Meter
A 5-segment LED level meter displays
the level of the composite (program and
interrupt) IFB signal. The three green
LEDs are lit with signals in the normal
operating range. The yellow LED lights
with a signal slightly higher than normal.
The red LED lights when signal levels are
in the “headroom” area. The ballistics of
the meter are a cross between that of a
VU and a peak (PPM) meter. (We affec-
tionately refer to it as a “PU” meter!)
The Model 770’s monitor section allows
the selection of IFB as it’s source. With
this selection the mechanical VU meter will
also display the IFB signal. With normal
IFB audio signal levels the mechanical VU
meter may seem to display a few dB lower
than that displayed on the IFB section’s