Studio Technologies 47 - Manual (Page 8)

Issue 1, August 2010 Model 47 User Guide
Page 8 Studio Technologies, Inc.
received from the 4-wire source and
two displaying the level being sent to
the 4-wire output. During installation and
setup the meters are invaluable in help-
ing to confirm that the nominal level DIP
switch settings have been properly made.
During normal operation the meters offer
rapid confirmation of audio signal flow
in and out of the unit. Additional LED
status indicators are also provided, offer-
ing a clear view of the 2-wire DC power
and auto null functions.
Pro Audio Quality
The Model 47’s audio circuitry was de-
signed in the spirit of professional audio
equipment, rather than that found in typi-
cal party-line intercom gear. High-perfor-
mance components are used throughout,
providing low-distortion, low-noise, and
high headroom. Using passive and active
filters, the frequency response is limited to
approximately 100 Hz to 8 kHz. This range
was selected to provide excellent perfor-
mance for human speech, while maxi-
mizing the ability of the hybrids to create
substantial “nulls.” When the Model 47’s
internal DC power sources are selected to
provide 2-wire party-line intercom power,
enhanced audio performance can also
be expected. The quality of the DC power
sources is excellent, with very little noise,
hum, or “hiss” being added to the 2-wire
connections.
Attention to detail is a hallmark of the
Model 47’s design. For example, during
the brief auto nulling process an interface
channel’s 4-wire input and output signal is
muted, preventing unwanted audio from
reaching the connected equipment. Asso-
ciated with the 2-wire interfaces is circuitry
that, under software control, applies 200
ohm terminating impedances to the 2-wire
party-line circuits. This, along with other
circuitry that monitors DC voltages pres-
ent on the 2-wire circuits, ensures that
audio instability associated with untermi-
nated circuits will rarely occur. As previ-
ously mentioned the Model 47’s 2-wire
DC power sources offer a unique level of
performance. Their ability to deliver power
while maintaining audio quality is simply
unmatched.
Special Applications
While the Model 47 is designed to directly
integrate into typical applications, it’s
ready to support the “one-in-a-million”
situations too. To accomplish this DIP
switches, accessible on the back panel,
allow some of the automatic features to
be disabled. For example, one DIP switch
allows the auto-terminate feature to be
disabled. While this feature can help
maintain audio quality, advanced users
might need to disable it. This would al-
low full control over the Model 47’s four
hybrid circuits, enabling them to be used
completely independently. A second DIP
switch changes the way in which the front-
panel auto null pushbutton switches oper-
ate. Normally pressing one of the buttons
begins the process of auto nulling both
channels associated with an interface.
The alternate switch mode allows each
auto null sequence to be activated inde-
pendently. One tap of the auto null button
will begin the auto null process for inter-
face one. Two taps of the button will begin
the auto null process for channel two.
For installer-selected applications, three
opto-coupled inputs allow selected Model
47 features to be remotely controlled.
These features include remote auto null-
ing for each interface and remote “mic kill”
activation.