Clear-Com Tempest2400 - Manual (Page 60)

54 Tempest®24 00 2 -Channel Wireless Intercom System
Auto-Null Explained
In 2-Wire intercom systems, ineffi 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 noti ceable, but when connected to an
extremely sensiti ve digital system, the echo becomes more problemati c.
In order to minimize echo resulti ng from connecti on to an external 2-Wire system, it is necessary to opti mize the hardware of the
hybrid circuitry in the Tempest BaseStati on. Tempest provides a user initi ated AUTO-NULL feature that automati cally opti mizes
the 2-Wire interface. Nulling only impacts 2-Wire hardwired intercom connecti ons.
Auto-Null sends a tone to each of the 2-Wire intercom channel connecti ons. The Tempest Wireless BaseStati on DSP monitors the
echo and adjusts the line characteristi cs (Resistance and Capacitance) to opti mize the interface to the external 2-Wire system.
When Auto-Null is initi ated, all of the functi ons of the BaseStati on including communicati on are interrupted. The Auto-Null
process takes approximately 10 seconds. Intercom levels may need to be adjusted aft er the 2-Wire intercom lines have been
nulled.
Auto-Null Procedure
Turn OFF all TALK butt ons on both the wired and wireless systems. Since Tempest monitors a self generated tone to adjust
the null characteristi 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 BeltStati ons, but the wired communicati on stati ons will need to be turned OFF individually, or a hardwired Mic
Kill signal will need to be initi ated.
On the Tempest BaseStati on press MENU to open the Main Menu. Rotate the Volume Control to scroll through the menu
opti ons to the “Wired Intercom Setti ngs” and select “Auto-Null.” Select “Null Now” to start the Auto-Null process. Normal
functi ons will be interrupted for about 10 seconds during the Auto-Null process. Progress of the null process can be
observed on the BaseStati on LCD display.
The BaseStati on display will indicate “Auto-Null Complete” once the Auto-Null process is completed. Press MENU to escape
to the Operati onal screen.
Acti vate Auto-Null for new connecti ons or whenever the 2-Wire system changes signifi cantly, such as when additi onal
wired belt packs are added or removed, or when cable lengths are changed signifi cantly.
Test for Echo
Talk into the wireless system for at least 10 seconds to test for echo. Echo Cancellati on (ECAN) soft 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 fi rst enabled, it requires up to 10 seconds for it to achieve convergence. There will usually be
some noti ceable echo during the fi rst few seconds of testi ng, but it will diminish over ti me as the ECAN soft ware converges
to an inaudible level. Brief louder acti ve audio can help accelerate effi ciency.
During Auto-Null, wired intercom users will hear the nulling tones and communicati on will
be interrupted. It is recommended that this feature should be used only during setup and
not during live events.
If multi ple BaseStati ons are connected by 2-Wire intercom connecti ons, each BaseStati on
must be nulled separately. Null one BaseStati on at a ti me.