AudioCodes Mediant 600 User Manual page 787

User's Manual
Parameter
Version 6.6
set to 1, it plays a ringback tone and sends 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
configured for ISDN / CAS doesn't play the ringback tone;
PI = 8 is sent in an ISDN Alert message (unless the
ProgressIndicator2ISDN_x parameter is configured
differently). If a 180 response is received, but the 'early
media' voice channel is not opened, the device configured
for CAS plays a ringback tone to the PSTN. The device
configured for ISDN 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 for ISDN trunks, this
option is applicable only if the LocalISDNRBSource parameter
787
52. Configuration Parameters Reference
Description
Mediant 600 & Mediant 1000