Clear-Com Tempest 900 Reference Manual

52 Tempest®900 4-Channel Wireless Intercom System
Auto-Null Explained
In 2-Wire intercom systems, ineciencies in the hybrid circuitries that combine or separate the send and receive audio signals
onto the same pair of wires inherently cause echo. Within analog systems the echo is not noceable, but when connected to an
extremely sensive digital system, the echo becomes more problemac.
In order to minimize echo resulng from connecon to an external 2-Wire system, it is necessary to opmize the hardware of the
hybrid circuitry in the Tempest BaseStaon. Tempest provides a user iniated AUTO-NULL feature that automacally opmizes
the 2-Wire interface. Nulling only impacts 2-Wire hard wired intercom connecons.
Auto-Null sends a tone to each of the 2-Wire intercom channel connecons. The Tempest Wireless BaseStaon DSP monitors the
echo and adjusts the line characteriscs (Resistance and Capacitance) to opmize the interface to the external 2-Wire system.
When Auto-Null is iniated, all of the funcons of the BaseStaon including communicaon are interrupted. The Auto-Null
process takes approximately 10 seconds. Intercom levels may need to be adjusted aer the 2-Wire intercom lines have been
nulled.
Auto-Null Procedure
Turn OFF all TALK buons on both the wired and wireless systems. Since Tempest monitors a self generated tone to adjust
the null characteriscs, any sounds entering through either the wired or wireless intercom systems will interfere with the
nulling process. When the Auto-Null or Manual Null menu screens are accessed, Tempest sends a Mic Kill signal to all
wireless BeltStaons, but the wired communicaon staons will need to be turned OFF individually, or a hard wired Mic
Kill signal will need to be iniated.
On the Tempest BaseStaon press MENU to open the Main Menu. Rotate the Volume Control to scroll through the menu
opons to the “Wired Intercom Sengs” and select “Auto-Null.” Select “Null Now” to start the Auto-Null process. Normal
funcons will be interrupted for about 10 seconds during the Auto-Null process. Progress of the null process can be
observed on the BaseStaon LCD display.
The BaseStaon display will indicate “Auto-Null Complete” once the Auto-Null process is completed. Press MENU to escape
to the Operaonal screen.
Acvate Auto-Null for new connecons or whenever the 2-Wire system changes signicantly, such as when addional
wired BeltStaons are added or removed, or when cable lengths are changed signicantly.
Test for Echo
Talk into the wireless system for at least 10 seconds to test for echo. Echo Cancellaon (ECAN) soware is disabled in the
Auto-Null and Manual Null screens to ensure the best hardware null. Press MENU to exit the nulling menu screen, and to
enable ECAN. When ECAN is rst enabled, it requires up to 10 seconds for it to achieve convergence. There will usually be
some noceable echo during the rst few seconds of tesng, but it will diminish over me as the ECAN soware converges
to an inaudible level. Brief louder acve audio can help accelerate eciency.
During Auto-Null, wired intercom users will hear the nulling tones and communicaon will
be interrupted. It is recommended that this feature should be used only during setup and
not during live events.
If mulple BaseStaons are connected by 2-Wire intercom connecons, each BaseStaon
must be nulled separately. Null one BaseStaon at a me.

Clear-Com Tempest 900 Specifications

General

Brand	Clear-Com
Model	Tempest 900
Category	Intercom System
Language	English