Studio Technologies 2A 2013 - Manual (Page 24)

Issue 1, October 2013 Model 2A User Guide
Page 24 Studio Technologies, Inc.
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 mi-
crophone 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 example 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 sophisti-
cated 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, re-
ceive audio from telephone interface 1, or
receive audio from telephone interface 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 as-
signed to one of the IFB channels. VOX
interrupt activity can be noted by observing
the yellow VOX LED associated with the as-
signed 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 whenever the inter-
face 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 set for the telephone line
mode and DC current is flowing through
the interface.
The interface control switch, active only
in the telephone line mode, allows the
interface to be answered (taken “off hook”)
or hung up (placed “on hook”). Momentarily
pressing the switch to its up position,
labeled ANSWER, places the interface in
its active or off-hook state. If loop current
is detected, the interface will stay in its
off-hook state and the loop current LED
will light. If loop current is not detected, the
interface will return to its off-hook (idle)
state after a few seconds. Momentarily
pressing the switch to the down position,
labeled HANG UP, immediately disconnects
the interface from the telephone line.
Telephone line audio signals can vary great-
ly in level on a call-by-call basis. To counter
this problem, a level trim potentiometer is
provided for the operator, allowing adjust-
ment over a ±8 dB range. A quiet signal
can be boosted, and a “hot” signal can be
attenuated. The trim pot is accessible via a
small hole in the front panel, directly to the
right of the interface control switch. Using
an Xcelite® “greenie” straight-blade screw
driver is recommended.
Telephone Interface 2
Two status LEDs, two switches, and one trim
potentiometer are associated with telephone
interface 2, labeled TELCO 2. The yellow