Studio Technologies 5132 2014 - Manual (Page 14)

Issue 5, October 2014 Model 5132 User Guide
Page 14 Studio Technologies, Inc.
Model 5132
Party-Line Interface Module
DC Voltage Monitoring
The Pin 2 Status LED can be a highly
useful “tool” for understanding the status
of the party-line intercom connection. It
does this by providing an indication of
the DC voltage that is present on pin 2
(with respect to pin 1) of the Model 5132’s
party-line interface connector. The Model
5132’s microcontroller integrated circuit,
under software control, “watches” to en-
sure that the DC voltage present on pin 2
of the party-line intercom interface is at an
acceptable level for the selected operat-
ing state. When the Model 5132’s internal
party-line power source is enabled 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 tempo-
rary over-current or short-circuit condition,
such as when defective cables are used to
interconnect user devices to the party-line
intercom interface.
If the Model 5132 is selected for use with
an external party-line circuit the Pin 2
Status LED will function in a slightly differ-
ent way. It will light whenever the signal on
pin 2 is greater than approximately 18 volts
DC. The LED will not light if the voltage
is less than 18 volts DC. The status LED
functions will allow a user to quickly deter-
mine if an active party-line circuit has been
connected.
Fault Condition
If the Model 5132 is providing party-line
power and an under-voltage condition is
present for a continuous 1-second period
it will cause a fault condition to be recog-
nized. The Pin 2 Status LED will indicate
this condition by changing from being con-
tinuously lit to flashing. In addition, the out-
put voltage on the internal party-line power
supply circuit will automatically shut down.
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 continu-
ous short circuit presented to the party-line
intercom connector will result in a continu-
ous 4-seconds-on, 5-seconds-off error
cycle. It’s important to note that during the
5-second-off period no voltage monitoring
takes place. Removing the fault condition
will not result in the output voltage immedi-
ately turning on again; the 5-second shut-
down period must first elapse.
Technical Notes
Maintaining Correct Input
Signal Levels
The Model 5132’s line-level audio inputs
and outputs are designed for compat-
ibility with either SMPTE (5132S) or EBU
(5132E) audio level standards. Applying
signals to these audio inputs at a signifi-
cantly lower level than the intended nomi-
nal will reduce 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 re-
duce the headroom and greatly increase
the chance of reaching audio “clipping.”
Obviously, these cautions are not unique
to the Model 5132, but apply to most audio
equipment. The front-panel level meters
provide an easy means of confirming that
a Model 5132 is being presented with the
correct audio levels.