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M-LA Technical Developments
DEFAULT WIDE AREA TRUNKING
by Steve Non-mod and Kurt Stefans
ABSTRACT
the site can be equipped with a sensing mechanism to detect the default condition based on the absence of control signals from the Zone Controller and the presence of the audio switch. As a second option, the zone controller itselfcan be programmed to detect the default condition and, in response, provide a "default condition" signal to all sites. With this lat- ter option, therefore, the site would merely detect the default condition signal aa provided from the Zone Controller and, in response, switch into the default mode.
To allow the sites to facilitate minimal trunking communications, contention, and the presence ofthe audio switch, an inaudible signal is injected on the audio path by the transmitting site and decoded by the receiving site.
Further, the audio switch would be provided with a list of all default channels for all sites. The audio switch would also be provided with a means of deter- mining when the default condition exists. This means it would be the same as above, namely, the tirst option whereby the audio switch detects the default condi- tion based on the absence of control signals from the Zone Controller, and the second option whereby the Zone Controller provides a dedicated default con- dition signal to the audio switch.
Once in the default condition, the audio switch would route all default signals from all sites to the predetermined location, for example, a console operator.
The default audio routing will return to normal once the proper signal is sent to the sites from the audio switch or the proper inaudible signals are no longer detec...