Performing Manual D-Channel Switchover In Nfas Group; Isdn Overlap Dialing; Collecting Isdn Digits And Sending Complete Number In Sip - AudioCodes Mediant 600 User Manual

21.6.4 Performing Manual D-Channel Switchover in NFAS Group

If an NFAS group is configured with two D-channels (Primary and Backup), you can do a
manual switchover between these D-channels.

To manually switchover from active to standby D-channel:
1. Open the NFAS Group & D-Channel Status page (Status & Diagnostics tab > VoIP
Status menu > NFAS Group & D-Channel Status).
2. Select the required NFAS group, and then click the Switch Activity button.
Notes:
21.7

ISDN Overlap Dialing

Overlap dialing is a dialing scheme used by several ISDN variants to send and/or receive
called number digits one after the other (or several at a time). This is in contrast to en-bloc
dialing in which a complete number is sent in one message. ISDN overlap dialing is
applicaable to PRI and BRI.
The device supports the following ISDN overlap dialing methods:

Collects ISDN called party number digits and then sends the SIP INVITE to the IP side
with the complete destination number (see 'Collecting ISDN Digits and Sending
Complete Number in SIP' on page 288)

Interworks ISDN overlap dialing with SIP, according to RFC 3578 (see 'Interworking
ISDN Overlap Dialing with SIP According to RFC 3578' on page 289)

21.7.1 Collecting ISDN Digits and Sending Complete Number in SIP

The device can support an overlap dialing mode whereby the device collects the called
party number digits from ISDN Q.931 Information messages or DTMF signals, and then
sends a SIP INVITE message to the IP side containing the complete destination number.
ISDN overlap dialing for incoming ISDN calls can be configured for the entire device or per
E1/T1 trunk. This is configured using the global, ISDNRxOverlap parameter or the
ISDNRxOverlap_x parameter (where x denotes the trunk number), respectively.
By default (see the ISDNINCallsBehavior parameter), the device plays a dial tone to the
ISDN user side when it receives an empty called number from the ISDN. In this scenario,
the device includes the Progress Indicator in the SetupAck ISDN message that it sends to
the ISDN side.
The device can also mute in-band DTMF detection until it receives the complete
destination number from the ISDN. This is configured using the MuteDTMFInOverlap
parameter. The Information digits can be sent in-band in the voice stream, or out-of-band
using Q.931 Information messages. If Q.931 Information messages are used, the DTMF in-
band detector must be disabled. Note that when at least one digit is received in the ISDN
Setup message, the device stops playing a dial tone.
The device stops collecting digits (from the ISDN) upon the following scenarios:

The device receives a Sending Complete IE in the ISDN Setup or Information
messages, indicating no more digits.

The timeout between received digits expires (configured by the TimeBetweenDigits
User's Manual
•
The Switch Activity button is unavailable (i.e, grayed out) if a switchover
cannot be done due to, for example, alarms or unsuitable states.
•
This feature is applicable only to T1 ISDN protocols supporting NFAS,
and only if the NFAS group is configured with two D-channels.
288
Mediant 600 & Mediant 1000
Document #: LTRT-83313