ARA-1 Operations Manual
3-10
INTEROPERABILITY NOW
3.3.1.4
Radio COR VOX Hang Time
When using VOX as the Radio COR Type, the system depends on the presence of audio to
consider a signal present. Since speech is not continuous (there are pauses in it), the VOX system
must “hang,” or wait for a certain period of time, before making the determination that the signal
is no longer present, otherwise it will resquelch momentarily between syllables or during short
pauses in speech. Set the
Radio COR VOX
Hang Time
to the lowest level that does not create
inappropriate resquelching. The ARA-1 front panel
CHANNEL ACTIVE
LED is lit whenever the
ARA-1 has detected active COR from the radio or its Radio VOX function has been tripped. If
this LED flashes during pauses in speech from the radio, the hang time must be increased.
3.3.2
Radio PTT Timeout
The
Radio PTT Timeout
option sets the maximum amount of time (in seconds) that the ARA-1
will continuously assert PTT. Its purpose is to protect the radio’s transmitter from damage as
well as to prevent radio users from being locked out by a “hung” PTT. When the PTT timeout
triggers, the original source of the PTT (Network COR) must clear (de-activate) before that
source will be allowed to again activate the ARA-1’s PTT output to the radio.
For example, if a user is connected to an ARA-1 via a SIP Phone, and the ARA-1 is configured
to use VMR as the Network COR Type, an overly sensitive SIP Phone microphone and/or loud
background voices can cause the ARA-1 to key indefinitely, thereby preventing any return
communications from radio users. The PTT Timeout will trigger after the set amount of time has
passed, unkeying the associated radio regardless of network audio content. Furthermore, the
ARA-1 will not allow network audio input to key the radio again until there is a break in the
network COR signal generated by the VMR function.
3.3.3
COR Priority
Since radios are half-duplex devices (you can either talk or listen, but not both at the same time),
the possibility exists that the radio may be receiving a signal at the same time a signal is being
received from the SIP network. The
COR Priority
setting allows the user to select which one has
priority. When set to
Radio Priority
, the radio RX audio takes precedence. That is, if the radio is
unsquelched (COR active), audio from the network will not put the radio into transmit mode until
the radio squelches (COR inactive). This means that people communicating via radios will have
precedence over communications coming in via the SIP network.
When set to
Network Priority
, valid audio from the network will key the radio associated with
the ARA-1 regardless of any RF signals being received by the radio.
For applications where full-duplex operation is desired, set this option to
Disable
. In this case,
neither the radio COR nor network COR will take priority, allowing both to pass through
unabated.
3.3.4
Always Pass Audio
By default, the ARA-1 will only pass audio from the radio interface to the network interface or
vice versa when the appropriate COR is present. In some applications, it may be desirable to have
audio pass through regardless of COR status, such as in full-duplex systems. Use the
Always Pass
Audio
option to enable audio pass through. Be sure you understand the concept of Silence
Suppression as it relates o COR/PTT before modifying, particularly for half-duplex systems.