AudioCodes Mediant 2000 User Manual page 327

SIP User's Manual
Parameter
Version 5.8
device configured with CAS to play an RBT (unless
SIP183Behaviour is set to 1).
The device configured with ISDN protocol type operates
according to the parameter LocalISDNRBSource:

If the device receives a 180 Ringing response (with or
without SDP) and LocalISDNRBSource is set to 1, it
plays an RBT and sends an Alert with PI = 8 (unless
the parameter ProgressIndicator2ISDN_ID is
configured differently).

If LocalISDNRBSource is set to 0, the device doesn't
play an RBT and an Alert message (without PI) is sent
to the ISDN. In this case, the PBX/PSTN plays the
RBT to the originating terminal by itself.
Note: Receipt of a 183 response does not cause the
device with ISDN protocol type to play an RBT; the
device issues a Progress message (unless
SIP183Behaviour is set to 1). If SIP183Behaviour is
set to 1, the 183 response is handled the same way as
a 180 Ringing response.

[2] Prefer IP = Play according to 'Early Media'. If a SIP 180
response is received and the voice channel is already open
(due to a previous 183 early media response or due to an
SDP in the current 180 response), the device with
ISDN/CAS protocol type doesn't play the RBT; PI = 8 is
sent in an ISDN Alert message (unless the parameter
ProgressIndicator2ISDN_ID is configured differently).
If a 180 response is received, but the 'early media' voice
channel is not opened, the device with CAS protocol type
plays an RBT to the PSTN. The device with ISDN protocol
type operates according to the parameter
LocalISDNRBSource:

If LocalISDNRBSource is set to 1, the device plays an
RBT and sends an ISDN Alert with PI = 8 to the ISDN
(unless the parameter ProgressIndicator2ISDN_ID is
configured differently).

If LocalISDNRBSource is set to 0, the device doesn't
play an RBT. No PI is sent in the ISDN Alert message
(unless the parameter ProgressIndicator2ISDN_ID is
configured differently). In this case, the PBX/PSTN
should play an RBT tone to the originating terminal by
itself.
Note: Receipt of a 183 response results in an ISDN
Progress message (unless SIP183Behaviour is set to
1). If SIP183Behaviour is set to 1 (183 is handled the
same way as a 180 + SDP), the device sends an Alert
message with PI = 8, without playing an RBT.

[3] Play tone according to received media. The behaviour
is similar to [2]. If a SIP 180 response is received and the
voice channel is already open (due to a previous 183 early
media response or due to an SDP in the current 180
response), the device plays a local RBT if there are no
prior received RTP packets. The device stops playing the
local RBT as soon as it starts receiving RTP packets. At
this stage, if the device receives additional 18x responses,
it does not resume playing the local RBT.
Note: For ISDN trunks, this option is applicable only if
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6. Configuration Parameters Reference
Description
October 2009