Studio Technologies 47A - Manual (Page 10)

Issue 1, September 2014 Model 47A User Guide
Page 10 Studio Technologies, Inc.
out that in many applications only a small
number of user devices, such as beltpacks,
are typically connected to 2-wire party-line
intercom circuits. But power on both pins 2
and 3 of each interface was necessary for
compatibility with SAP panel applications.
By adding two DC power sources to each
of the Model 47A’s 2-wire interfaces, the
need for external intercom power supplies
could often be eliminated.
The final step was to create a physical
package that would provide significant
resources in a form that allowed simple
and reliable integration with other equip-
ment. This was accomplished by including
two 2-channel interfaces in a 1U enclosure.
Using standard 3-pin XLR audio connec-
tors would enable rapid installation and
troubleshooting. And by making the Model
47A “universally” powered, installation in
any locale could be directly supported.
Installation
In this section you will be installing and
interconnecting the Model 47A. The one-
rack-space unit will be mounted in an
equipment rack. Audio input, audio output,
and party-line intercom connections will be
made by way of 3-pin XLR connectors. AC
mains power will be connected by means
of a detachable cord set that is compatible
with the Model 47A’s 3-pin IEC 320 C14
inlet connector.
System Components
The shipping carton contains the Model
47A Interface, user guide, and AC mains
cord suitable for use in North America and
Japan. Your dealer or distributor should
provide an AC mains cord appropriate for
use in other locations.
Locating the Model 47A
The Model 47A’s mounting location will
dictate the length of the cable runs needed
to link the unit with the connected devices.
This is really only a factor in relation to the
2-wire party-line intercom circuits. These
circuits carry unbalanced audio which can
be susceptible to interference and cross-
talk issues. Intercom circuits also carry DC
power which may make resistive losses
come into the picture. In general, shorter
intercom cable lengths will assure more re-
liable and consistent system performance.
Another location criterion is access to the
Model 47A’s front panel. An optimal loca-
tion will allow convenient use of the auto
null pushbuttons and easy observation of
the status and level meter LEDs.
Mounting the Model 47A
Once a mounting location has been select-
ed installation can begin. The Model 47A
requires one space (1.75 vertical inches)
in a standard 19-inch (48.3 cm) equipment
rack. Secure the unit into the equipment
rack using two mounting screws per side.
4-Wire Audio Inputs and
Outputs
Two audio line input and two audio line
output signals are associated with the
4-wire section of each of the Model 47A’s
two interface circuits. Connections are
made using standard 3-pin male and
female XLR connectors. Refer to Appendi-
ces A, B, and C for details on interconnect-
ing with RTS, Riedel, and Clear-Com matrix
intercom systems.
4-Wire Line Inputs
As previously mentioned, each of the
Model 47A’s two interfaces allows two