Studio Technologies 2A 2015 - Manual (Page 25)

Model 2A User Guide Issue 2, March 2015
Studio Technologies, Inc. Page 25
The program level control allows the pro-
gram audio signal to be adjusted relative to
the interrupt audio level. The interrupt level
is internally fixed and serves as the refer-
ence. The gain structure was configured so
that the level control set for about 70 per-
cent of rotation (the “2-o’clock” position) will
give a program level approximately equal to
the interrupt level. This statement is made
under the assumption that a +4 dBu pro-
gram signal is selected and its associated
input trim pot is correctly set.
The 5-segment LED level meter displays
the internal level of the composite (program
and interrupt) IFB signal. The three green
LEDs are lit when the signal level is in the
normal operating range. The yellow LED will
light when signal level are slightly higher
than average. The red LED lights when
signal levels reach the “headroom” area.
The ballistics of the meter is a cross be-
tween that of a VU meter and a peak (PPM)
meter. (We affectionately refer to it as a
“PU” meter!) The meter should prove useful
during installation and maintenance, as well
as during normal operation.
A typical interrupt signal will light the green
LEDs, with peaks lighting the yellow LED.
The internal compressor circuit will keep
most interrupt signals from lighting the red
LED. When an interrupt is not taking place
the level meter will reflect the level of the
program audio source. Setting the program
level control to occasionally light the yellow
LED will give a program level approximately
equal to the interrupt level.
Voice Operated (VOX) Interrupt
The Model 2A contains a specialized func-
tion that allows an audio signal to auto-
matically interrupt the program signal. By
contrast, using the Model 2A’s internal
microphone requires an explicit action
by the operator, i.e., pressing a button to
cause an interrupt. In some cases, this
explicit action is simply not possible. An ex-
ample would be a director giving cues via
a 2-way radio or a telephone line. The VOX
circuitry creates an interrupt control signal
by detecting energy in the voice band. This
control signal acts on the selected IFB
channel, interrupting program audio and
routing VOX audio in its place. The VOX
interrupt can be assigned to either IFB
channel 1 or IFB channel 2, but not to both
simultaneously.
The VOX interrupt function is only sophis-
ticated from an internal-circuitry stand
point. Operation is quite simple, with only
two switches to set. The input switch is
used to select which of the three possible
audio sources are to be used by the VOX
circuit: audio from the auxiliary audio input,
receive audio from telephone interface
1, or receive audio from telephone inter-
face 2. The output switch is used to select
whether the VOX interrupt function is off
(not used), assigned to interrupt channel
1, or assigned to interrupt channel 2. VOX
operation can commence as soon as the
output is assigned to one of the IFB chan-
nels. VOX interrupt activity can be noted by
observing the yellow VOX LED associated
with the assigned IFB channel.
Telephone Interface 1
Two status LEDs, one switch, and one
trim potentiometer are associated with
telephone interface 1, labeled TELCO 1.
The yellow LED, labeled STD, is lit when-
ever the interface is set for the standard
audio mode by the switch on the back
panel. The red LED, labeled LC for loop
current, lights any time the interface is