Studio Technologies 5130 2013 - Manual (Page 12)

Issue 5, July 2013 Model 5130 User Guide
Page 12 Studio Technologies, Inc.
Model 5130
Party-Line Interface Module
devices such as the RTS BP325 are di-
rectly compatible and will provide excellent
performance. Up to three of these units
can typically be supported.
For reference, this paragraph provides de-
tails on the signals that are present on the
party-line intercom interface’s 3-pin male
XLR connector. Pin 1 provides common
for power and audio; pin 2 has 28 volts DC
with channel 1 audio; pin 3 has channel 2
audio. The nominal audio output level on
the two channels is –10 dBu, no matter if
the module is a 5130S or a 5130E. The
maximum current draw from pin 2 to pin 1
is 180 milliamperes. The circuitry associ-
ated with pin 3 is protected from damage
should pin 2 (nominal 28 volts DC) be-
come accidentally connected to it.
DC Voltage Monitoring
The pin 2 power LED can be a highly use-
ful “tool” for understanding the status of the
party-line intercom connection. It does this
by proving an indication of the DC voltage
that is present on pin 2 (with respect to pin
1) of the Model 5130’s party-line interface
connector. The Model 5130’s microcon-
troller integrated circuit, under software
control, “watches” to ensure that the DC
voltage present on pin 2 of the party-line
intercom interface is at an acceptable level.
The under-voltage threshold for pin 2 is 24
volts. This is four volts less than the normal
level of 28 volts DC. The LED will “flash” at
a moderate cadence if the voltage on the
interface falls below the acceptable 24 volt
value. This can be caused by a temporary
over-current or short-circuit condition, such
as when interconnecting user devices to
the party-line intercom interface using por-
table cabling.
Fault Condition
If the Model 5130 is in an under-voltage
condition that’s present for a continuous
1-second period it will cause a fault condi-
tion to be recognized. The pin 2 power LED
will indicate this condition by changing from
being continuously lit to flashing. In addition,
the output voltage on the party-line power
supply 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 pre-
sented to the party-line intercom output
will result in a continuous 4-seconds-on,
5-seconds-off error cycle. It’s important to
note that during the 5-second-off period no
voltage monitoring takes places. Removing
the fault condition will not result in the out-
put voltage immediately turning on again;
the 5-second shut-down period must first
elapse.
Technical Notes
Maintaining Correct Input
Signal Levels
The Model 5130’s 4-wire audio inputs and
outputs are designed for compatibility with
either SMPTE (5130S) or EBU (5130E)
audio level standards. Applying signals to
these audio inputs at a significantly lower
level than the intended nominal will re-
duce the signal-to-noise ratio (raising the
perceived noise floor) and can prevent the
connected user devices from operating
optimally. Applying signal levels significantly
higher than nominal will reduce the head-
room and greatly increase the chance of