Studio Technologies 2A 2013 - Manual (Page 29)

Model 2A User Guide Issue 1, October 2013
Studio Technologies, Inc. Page 29
5. Use the front-panel program select
switches to select, one at a time, the
four program inputs. The line output
should give an output level of +4 dBu
nominal, with +8 to +12 dBu probable on
peaks. The actual output level is not im-
portant and a lower level is much better
than a “hotter” average level.
6. After observing the relative strengths
of the four sources, use one or more of
the trim pots, if required, to get an equal
average level from the four sources.
7. If you don’t have an audio level meter
handy, or if you’re not concerned about
exact calibration, use one of the LED
level meters on the front panel to set the
trim pots. Actually, if your ears are pretty
good use them, and no meters, to set
the trim pots to get equal levels. That’s
what we would do if we were in the field!
Confirm your subjective adjustment with
the LED meter and you should be set.
Setting the Line-level Trim Pot
on the Model 22 and Model 24
Access Stations
The Model 22 and Model 24’s line input
circuitry allows balanced and unbalanced
signals with a nominal level of –15 to +10
dBu to be correctly interfaced. The system
is designed to have an access station send
interrupt signals at a signal level of –10
dBu to the Model 2A Central Controller.
A level adjustment trim pot on the Model
22 and Model 24 allows the various signal
levels to be adjusted to give the desired
signal strength. Set the trim pot only after
installing the Model 2A and associated
Model 22 and Model 24 units. The calibra-
tion procedure is as follows:
1. Begin by connecting an audio level
measuring device across the test points
labeled COM and AUDIO on the Model
22 or Model 24’s circuit board. Set the
meter to display the audio signal level in
terms of dBu, i.e., level in dB referenced
to 0.7746 volts RMS with no defined
load impedance.
2. While speaking into the microphone,
headset, or other device that produces
the line-level signal, adjust the trim
pot to give an average level of approxi-
mately –10 dBu as shown on the meter.
Peak signals should fall in the –5 to
0 dBu range. This trim pot setting should
result in a clean, clear interrupt signal,
without excess compressing by the
Model 2A’s circuitry.
Safety Warning
A competent technician is required to
perform any configuration changes that
entail accessing the Model 2A’s circuit
board. The cover of the Model 2A must
be removed, exposing the technician to
a potential shock hazard. Only after AC
mains power has been disconnected and
the mains cord removed from the back
of the Model 2A should the cover be re-
moved. Four screws, two on each side of
the chassis, are used to secure the cover.
Configuring Auto Answer
From the factory the auto answer func-
tion associated with telephone interface 2
(TELCO 2) will typically be configured to
answer after detecting one cycle of ringing
voltage. This setting may be appropriate
for most applications. But some may ben-
efit from an alternate configuration. Two
switches, part of a 4-position DIP switch
assembly, allow the auto answer function