Studio Technologies 5121 - Manual (Page 11)

Model 5121 User Guide Issue 3, October 2014
Studio Technologies, Inc. Page 11
Model 5121
Line/IFB Output Module
themselves; a very small party line indeed,
but possibly a useful one too.
The signals that are present on the IFB
output’s 3-pin male XLR connector are typi-
cal for broadcast powered “wet” IFB circuits.
Pin 1 is common for power and audio, pin 2
is 28 volts DC with channel 1 audio modu-
lated on it, and pin 3 is channel 2 audio.
The nominal audio levels on the IFB chan-
nels are –10 dBu, no matter if the module
is a 5121S (SMPTE version) or a 5121E
(EBU version). The maximum current draw
from pin 2 to pin 1 is 120 milliamperes. The
circuitry associated with pin 3 is protected
from damage should pin 2 (28 volts DC) be
accidentally connected to it.
DC Voltage Monitoring
The Model 5121’s microcontroller integrated
circuit, under firmware control, “watches” to
ensure that the DC voltage present on pin 2
of the IFB output is at an acceptable level.
The low-voltage threshold for the Model
5121’s nominal 28 volt DC output is 24 volts.
The DC Pin 2 status LED provides an indi-
cation of the DC voltage on the IFB output’s
XLR connector. The LED will “flash” at a
moderate cadence if the voltage on the IFB
circuit falls below the acceptable value. This
can be caused by a temporary over-current
or short-circuit condition, such as when in-
terconnecting user devices to the IFB circuit
using portable cabling.
An under-voltage condition that’s present for
a continuous 1-second period will cause a
fault condition to be recognized. The status
LED will indicate this condition by flash-
ing at a faster rate. In addition, the output
voltage on the IFB circuit will automatically
shut down to an essentially off condition. A
5-second “cool-down” period will then take
place, after which the output voltage will
again become active. As soon as the output
is enabled normal output voltage monitoring
will again take place. A continuous short-
circuit presented to the IFB output will result
in a continuous 4-seconds-on, 5-seconds-
off error cycle. It’s important to note that
during the 5-seconds-off period no voltage
monitoring takes places. Removing the fault
condition will not result in the output voltage
immediately turning on again; the 5-second
shut-down period must first elapse.
Remote Monitoring and
Control
Several of the Model 5121’s functions are
capable of being monitored and controlled
remotely. Implementing these functions
requires use of a Studio Technologies
Model 5190 Remote Access Module. The
two modules, along with up to 15 more, will
interconnect using a local RS-485 data bus.
The remote monitoring functions include ob-
serving the status of the IFB DC output and
viewing the version number of the Model
5121’s firmware (embedded software). The
remote control capability includes input
source selection and input source level. By
default the automatic input source selection
mode will be active. In this mode the digital
input source will take precedence over the
analog input source. If a digital audio input
signal is connected and “locked” with the
input circuitry its two audio channels will be
used as the Model 5121’s audio sources.
The audio sources can also be selected to
always use the digital input or always use
the analog input.
The gain of the two audio channels can
be independently adjusted over a range of
±12 dB in 3 dB steps with the default set-
ting being 0 dB. The selected value applies
whether the audio source comes from the