ARA-1 Operations Manual
INTEROPERABILITY NOW
3-11
3.3.5
Network COR Settings Options
Network COR
settings define how and when the audio coming from the network is seen to be
valid and, therefore, will cause the associated radio to “key up” and transmit this audio. Also
affecting this is the
COR Priority
setting, which decides which has precedence—the radio or the
network—when valid audio is being received from both simultaneously (see Section 3.3.3).
Note: Packet COR/Silence Suppression is the preferred method, but requires that both Packet
COR and Silence Suppression are used by all SIP devices in the system.
Please see also Section 1.8 “COR & PTT Signaling in the SIP Environment.”
3.3.5.1
Network COR Type
The
Network COR Type
function is similar to
Radio COR Type
except that there are more options.
This setting tells the ARA-1 how to determine when there is a signal coming from the SIP
network, which will ultimately activate the attached transmitter. VOX senses the audio level,
while VMR (Voice Modulation Recognition) looks specifically for human speech and ignores
non-speech signals. VMR can help prevent false transmitter activation from background noise
on the SIP connection (such as someone breathing heavily into a SIP Phone handset mouthpiece,
or someone using a SIP Phone in a high ambient noise environment).
The
RTP Header
,
RTP VOX
, and
RTP VMR
options may be useful if multiple
ARA-1 units are integrated in the SIP network. These COR types make use of the ARA-1 RTP
extension header that sends the unit’s COR status to other ARA-1s that they are conferenced
with. This is helpful as these other ARA-1s will receive a positive indication of COR status that
arrives coincidentally with the radio audio, and the ARA-1 will not have to derive the COR status
using a VOX or VMR function. This is a quicker and surer way to determine when the linked
ARA-1s should key their associated transmitters. For these settings to have any utility on the unit
being configured to use them, another ARA-1(or other SIP device) that may link to this unit must
send the RTP Header. If the device on the other side of the network is another ARA-1, it must
have its SIP Settings
Send Radio COR/AUX Status
option enabled. See Section 3.2.3 for
instructions about enabling this function.
To further clarify, when Radio A is linked to Radio B over a SIP network via a pair of ARA-1s,
whenever Radio A is receiving a valid signal (and, therefore, has active COR), Radio B should
have its PTT activated so that it can retransmit the audio received from Radio A. If the ARA-1
associated with Radio A has the
Send Radio COR/AUX Status
function enabled, it will send its
COR status over the network as part of the RTP extension header. The ARA-1 associated with
Radio B can make use of this information only if its Network COR Type is set to one of the
following:
•
RTP Header
•
RTP VOX
•
RTP VMR
Use the
RTP Header
setting if all end-devices on the system are connected via ARA-1s or other
SIP interfaces that support the RTP Header. For example, if there will only be two radios
connected over the Internet (see the center diagram of Figure 1-3). When the Network COR Type
is set to
RTP Header
, the only method used to validate network audio (and hence key the
associated radio) is the COR information transferred in the RTP extension header. This means
that the ARA-1 will ignore network audio from other devices not interfaced by an ARA-1 with