AudioCodes Mediant 500L User Manual page 1187

User's Manual
Parameter
Version 7.2
an ISDN Alert with PI = 8 (unless the
ProgressIndicator2ISDN_x parameter is configured
differently).
2) If the LocalISDNRBSource parameter is set to 0, the
device doesn't play a ringback tone and an Alert
message without PI is sent to the ISDN. In this case,
the PBX / PSTN plays the ringback tone to the
originating terminal. Note that the receipt of a 183
response does not cause the device configured for
ISDN to play a ringback tone; the device issues a
Progress message (unless SIP183Behaviour is set to
1). If the SIP183Behaviour parameter is set to 1, the
183 response is handled the same way as a 180
Ringing response.

[2] Prefer IP = (Default):

Analog Interfaces: Plays a ringback tone to the Tel side
only if a 180/183 response without SDP is received. If
180/183 with SDP message is received, the device cuts
through the voice channel and doesn't play the ringback
tone.

Digital Interfaces: Plays 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 doesn't play the ringback tone; PI
= 8 is sent in an ISDN Alert message (unless the
ProgressIndicator2ISDN_x parameter is configured
differently).
ISDN: The device operates according to the
LocalISDNRBSource parameter:
1) If LocalISDNRBSource is set to 1, the device plays a
ringback tone and sends an ISDN Alert with PI = 8 to
the ISDN (unless the ProgressIndicator2ISDN_x
parameter is configured differently).
2) If LocalISDNRBSource is set to 0, the device doesn't
play a ringback tone. No PI is sent in the ISDN Alert
message (unless the ProgressIndicator2ISDN_x
parameter is configured differently). In this case, the
PBX / PSTN plays a ringback tone to the originating
terminal. Note that the 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 a ringback tone.

[3] Play Local Until Remote Media Arrive = Plays a ringback
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 ringback tone if there are no prior
received RTP packets. The device stops playing the local
ringback tone 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 ringback tone. Note that
1187
69. Configuration Parameters Reference
Description
Mediant 500L Gateway & E-SBC