Studio Technologies 47A - Manual (Page 16)

Issue 1, September 2014 Model 47A User Guide
Page 16 Studio Technologies, Inc.
As soon as AC mains power is applied
the Model 47A will begin its power-up
sequence. As a “boot up” indication the
power LED and each of the status LEDs
will momentarily light. After the sequence
has completed the power LED will again
light and remain lit. The unit is now fully
functional.
Configuration
For the Model 47A to support the needs
of specific applications a number of op-
erating parameters must be configured.
These include the 2-wire party-line power
source, the nominal 2-wire level, and the
nominal 4-wire level. Three 4-position DIP
switch assemblies are used to establish
the desired configuration. One DIP switch
assembly is associated with interface 1, a
second is associated with interface 2, and
a third is associated with advanced oper-
ating features that apply to both interfaces.
Configuration – Interface 1
and Interface 2
The DIP switch assemblies associated
with interfaces 1 and 2 are accessible on
the Model 47A’s front panel. They provide
identical capability for their respective
interfaces. Refer to Figure 5 for a detailed
view. In this section the four DIP switches
associated with interface 1 will be covered
in detail. This information applies to inter-
face 2 as well. The four DIP switches allow
selection of the 2-wire party-line power
sources, the nominal level for the 2-wire
party-line channels, and the nominal level
of the 4-wire inputs and outputs.
2-Wire Party-Line Power Source
DIP switch 1 is used to select whether or
not the Model 47A provides DC power to
pins 2 and 3 of connectors associated with
the 2-wire party-line intercom channels.
Two 3-pin male XLR connectors, one lo-
cated on the Model 47A’s front panel and
one on the back panel, are used to inter-
connect the Model 47A with the intercom
user devices or a SAP. When DIP switch 1
is in its off (down) position the Model 47A
will not provide DC power. This DIP switch
setting is appropriate when an external
intercom power supply is providing power
to the intercom circuit. In addition to power,
it’s expected that the external power supply
will also provide the required 200 ohm ter-
minating impedance to both pins 2 and 3.
When DIP switch 1 is in its on (up) posi-
tion the Model 47A provides independent
30 volt, 315 mA maximum sources of DC
power to pins 2 and 3 of the 2-wire PL
intercom connectors. The Model 47A will
also provide 200 ohm terminating imped-
ances for both pins 2 and 3 of the party-
line connectors. The DC power and termi-
nation capabilities allow direct powering
of 2-channel intercom beltpacks, such as
the RTS BP325. In addition, listen-only
Figure 5. Detail of front panel showing four DIP
switches