Studio Technologies 5132 2014 - Manual (Page 7)

Model 5132 User Guide Issue 5, October 2014
Studio Technologies, Inc. Page 7
Model 5132
Party-Line Interface Module
Two LEDs, located on the Model 5132’s
front panel, provide an indication of the
power source’s on/off state and the state
of the DC voltage present on pin 2 of the
party-line intercom XLR connector. Logic
circuitry contained within the Model 5132
monitors the voltage on pin 2. When the
Model 5132 is providing intercom power
this function will monitor pin 2 for a low-
voltage/over-current condition. If detected,
the DC output will automatically enter a
protection mode. Once the fault condition
is removed normal operation will again
resume. When an external source of inter-
com power is present the Pin 2 Status LED
offers the user a simple “go/no go” indica-
tion for rapid troubleshooting.
Analog Hybrids with Auto
Nulling
The 2-wire-to-4-wire hybrids provide low
noise, low distortion, good frequency
response, and high return-loss (“nulling”),
even when presented with a wide range
of party-line conditions. Unlike telephone-
line (“POTS”) oriented DSP-based hybrid
circuits, the Model 5132’s analog circuitry
maintains extended frequency response.
With this wide audio bandwidth, natural-
sounding voice signals can be sent to, and
received from, the connected party-line
user devices. This bandwidth also allows
high-frequency “call light” and “mic kill”
signals to pass through to connected
equipment.
The Model 5132’s sophisticated auto null-
ing function uses analog circuitry under
microprocessor control to achieve sig-
nificant trans-hybrid loss. This return-loss
“null” is achieved by making a series of
software-directed adjustments to account
for the resistive, inductive, and capacitive
conditions that are present on the connect-
ed party-line user devices and associated
cabling, as well as, if present, a connected
external intercom circuit. Whenever a user
presses the Model 5132’s Auto Null push-
button digital circuitry adjusts the 2-wire-
to-4-wire hybrids to achieve their maximum
return-loss for both interface channels.
The nulling process is automatic, last-
ing less than 15 seconds, and only takes
place upon user request. The resulting
null parameters are stored in non-volatile
memory.
Audio Inputs and Outputs
Two analog line-level inputs and outputs
are associated with the “4-wire” audio por-
tion of the Model 5132’s circuitry. These
are intended to interconnect with a variety
of devices, including matrix intercom sys-
tems, audio-over-fiber transport systems,
and specialized audio equipment. The
audio input and output circuitry is electroni-
cally balanced and capacitor coupled to
minimize the chance that hum, noise,
or interfacing issues will occur. The two
Model 5132 versions allow compatibility
with equipment that supports SMPTE
(+4 dBu) and EBU (0 dBu) analog audio
level standards.
Indicators
The Model 5132 contains four 5-segment
LED level meters. Two meters display the
level of the signals being received from the
party-line channels and two display the
level being sent to the party-line channels.
At the time of installation and setup the
meters are invaluable in helping to confirm
correct operation. During normal operation
the meters offer rapid confirmation of the
audio signals flowing into and out of the
module. Four additional LED indicators are