Studio Technologies 5130 2013 - Manual (Page 10)

Issue 5, July 2013 Model 5130 User Guide
Page 10 Studio Technologies, Inc.
Model 5130
Party-Line Interface Module
Operation
The Model 5130 is designed for continu-
ous operation with no internal adjustment,
calibration, or maintenance required.
The auto null function is used whenever
significant changes are made to the num-
ber of user devices or the interface cabling
connected to the party-line interface. It
also should be used if the characteristics
of a connected party-line intercom system
change. Activating the auto null function is
simple, only requiring the pressing of the
auto null pushbutton switch.
Maintaining the correct levels coming from
the 4-wire audio sources is very important.
This will ensure proper signal levels are
presented to party-line users and maintain
optimal audio fidelity. The audio level meters
and pin 2 power LED will assist users in
confirming that correct operation is taking
place. In addition, the under-voltage shut-
down function will help to protect the party-
line intercom power supply should a fault
condition be detected.
Auto Null
The Model 5130 contains circuitry to auto-
matically null the two 2-wire-to-4-wire inter-
faces. Normally this process is performed
at the time of initial Model 5130 user set up
and operation, but there’s no reason why
“auto nulling” can’t be initiated anytime one
desires. The only time that auto null must be
performed is if conditions have changed vis-
à-vis the party-line intercom user devices
and wiring connected to a Model 5130’s
party-line intercom interface connector.
Even a slight change to a party-line inter-
com circuit, such as adding or removing a
section of cable, is sufficient to require that
the auto null process be performed.
A pushbutton switch, located on the Model
5130’s front panel, is used to activate the
auto null process. To initiate auto null re-
quires simply pressing and releasing (“tap-
ping”) the button. An LED provides a visual
indication of the auto null process, flashing
when the auto null process is active. The
sequence takes less than 15 seconds to
complete.
An auto null sequence begins with the mut-
ing of the 4-wire audio input and output sig-
nal paths. This is followed by a short period
of 24 kHz signal that is sent out both the
party-line intercom interface channels. This
will turn off microphones on those connect-
ed user devices that are compatible with
the RTS TW-series “mic kill” protocol. The
actual auto nulling process is performed
next. A series of tones will be sent out the
party-line interface channels. Other Model
5130 circuitry, under software control, will
rapidly perform adjustments to achieve the
best null possible. After the null adjustments
have been made the results are stored in
non-volatile memory. Once the process is
complete the audio input and output paths
are again activated.
If possible, prior to performing an auto null
it’s polite to warn all personnel who are
actively using the connected party-line in-
tercom devices. The tones sent to the party-
line intercom channels during the nulling
process are not excessively loud or obnox-
ious, but most users might want to remove
their headsets during the process. In ad-
dition to warning users, it might be a good
time to ask them to mute any active micro-
phones. While the automatic “mic kill” signal
will apply to many user devices it may not
apply to all. Muting microphones is signifi-
cant as obtaining a “deep” null requires that
no extraneous signals be present on the
party-line circuit.