Studio Technologies 47 - Manual (Page 19)

Model 47 User Guide Issue 1, August 2010
Studio Technologies, Inc. Page 19
The auto terminate function should be
disabled only when absolutely necessary;
it’s possible that a significant downside
could be experienced. With auto terminate
disabled it’s important that properly ter-
minated 2-wire party-line intercom circuits
be connected to pins 2 or 3 on the Model
47’s 2-wire PL connectors. If they are not
connected, it’s likely that audio oscilla-
tions, noise, and distortion will be gener-
ated in the Model 47’s 2-wire-to-4-wire
converter circuitry. These audio artifacts
will not cause any damage, but will be
sent out the 4-wire line output connectors.
Users of the 4-wire equipment may be less
than pleased with what they hear!
Auto Null Button
One pushbutton switch is associated
with each of the Model 47’s two interface
circuits. An advanced configuration pa-
rameter allows selection of the button’s
operation. The choices are dual auto null
and independent auto null. When dual
auto null is selected a single tap (press
and release) of one of the two front-panel
pushbutton switches initiates a routine
that begins with channel 1’s auto null se-
quence taking place followed immediately
by channel 2’s auto null sequence being
performed. Note that the configuration
selected for auto null button operation will
also apply to the remote auto null inputs.
Independent auto null allows the auto null
function to be initiated for each channel as
desired. A single tap will start the auto null
routine for channel 1. Two taps will start
the routine for channel 2.
Referring to Figure 8, when DIP switch 2 is
in its off (down) position dual auto null is
selected. This is provided specifically for
cases where the Model 47’s 2-wire party-
line interfaces will be used with dual-chan-
nel intercom user devices. As an example:
the RTS TW-series provides two indepen-
dent audio channels, as well as power,
over a single 3-conductor cable. In a case
such as this it’s useful for both of the hy-
brid circuits associated with an interface to
be auto nulled at approximately the same
time. Dual auto null allows a single tap of
the button to initiate nulling of both hybrid
circuits.
When DIP switch 2 is in its on (up) position
independent auto null is selected. This
would be appropriate for applications in
which the two audio paths associated with
each interface are used with independent
party-line intercom circuits. This situation
might arise when two Clear-Com single-
channel intercom circuits are connected
to one of the Model 47’s dual-channel
interfaces. The hybrid circuit associated
with each channel can be auto nulled as
desired. Another example would be in
an RTS TW-series application that uses
source assignment panels. These SAP
panels would be used to route multiple
intercom channels to various sets of user
devices as desired. In this case, the two
channels associated with each Model 47
interface will often end up not routed to
the same user device; independent auto
nulling is certainly desired.
Figure 8. DIP Switch 2—Auto Null Button