Studio Technologies 5132 2012 - Manual (Page 7)

Model 5132 User Guide Issue 4, September 2012
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.
An automatic 4-wire mute function is ac-
tive whenever the Model 5132’s operating
mode has been set to support an external
party-line intercom circuit. (In this case
an external source of DC voltage and 200
ohm terminations is necessary for correct
operation.) The auto 4-wire mute function
helps to ensure that the Model 5132’s audio
interface circuitry will remain stable in “real-
world” situations. This unique feature makes
certain that if a valid party-line intercom
circuit is not detected objectionable audio
content, such as oscillations and “squeals,”
will not be sent to the associated 4-wire
equipment.
Analog Hybrids with Auto
Nulling
The 2-wire-to-4-wire hybrids provide low
noise, low distortion, good frequency re-
sponse, 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 4-wire
equipment.
The Model 5132’s sophisticated auto nulling
function uses analog circuitry under mi-
croprocessor control to achieve significant
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 condi-
tions that are present on the connected
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 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, lasting less than
15 seconds, and only takes place upon
user request. The resulting null parameters
are stored in nonvolatile memory.
Audio Inputs and Outputs
Two analog line-level inputs and two out-
puts are associated with the 4-wire portion
of the Model 5132’s circuitry. These are
intended to interconnect with a variety of
devices, including matrix intercom systems,
audio-over-fiber transport systems, and
specialized audio equipment. The audio in-
put and output circuitry is electronically bal-
anced and capacitor coupled to minimize
the chance that hum, noise, or interfacing
issues will occur. The two Model 5132 ver-
sions allow compatibility with equipment
that supports SMPTE (+4 dBu) and EBU
(0 dBu) analog audio level standards.