User guide

Port configuration VoIP phone ports
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iMG/RG Software Reference Manual (Voice Service)
• Telecom tone management and DTMF relay.
• This is a SIP protocol dependent solution used to transfer DTMF tones out-of-band either using SIP INFO
messages, or by means of RFC2833 ‘Named DTMF Events’ within the RTP stream. The underlying logic is as
follows:
• When the iMG attempts to establish a call, it adds RFC2833 ‘Named Telephone Event’ to the capabilities
listed for RTP packets, but only if a compressed codec (g726 or g729ab) has been configured for the
Voice access port involved in the call.
• If a call is then established using an uncompressed codec (i.e. g711u or g711a), the iMG will send DTMF
tones in-band - irrespective of whether or not the called endpoint supports RFC2833 Named Telephone
Events.
• If however a the call is established using a compressed codec, the iMG will send DTMF tones using
RFC2833 Named Telephone Events, but only if the called end-point supports this mechanism - otherwise
it switches to the same path used for voice (accepting DTMF distortion).
When the intelligent Multiservice Gateway is going to accept a call, it adds to the capabilities list the RTP packet
Named Telephone Event only if a compressed codec (g726 or g729ab) has been configured for the Voice access
port involved in the call.
• Then if the call is established using an uncompressed codec (i.e. g711u or g711a), the intelligent Multiservice
Gateway will send DTMF tone in-band (independently of whether the caller endpoint supports RTP packet
Named Telephone Event) on the same path used for voice.
• If the call is established using a compressed codec, the intelligent Multiservice Gateway will send DTMF
tones using RTP packet Named Telephone Event only if the caller end-point supports it, otherwise it
switches to the same path used for voice (accepting DTMF distortion).
• Inter-digit time/Inter-digit critical time.
Inter-digit time is the maximum acceptable time between the dialling of one digit and the next. If a time
longer than the Inter-digit time elapses after the dialling of a digit, dialling is considered complete. The timer
‘T’ in the digit map expression uses the Inter-digit time value. To change the value of the Inter-digit time use
the VOIP EP ANALOGUE SET IDT-PARTIAL command.
Inter-digit critical time is the maximum acceptable time between the off-hook event and the dialling of the
first digit. If a time longer than this has elapsed since off-hook and dialling has not yet started, then the con-
nection is closed and a busy tone is generated. To change the value of the Inter-digit critical time use the
VOIP EP ANALOGUE SET IDT-CRITICAL command.
• Off-hook time / On-hook time / Flash-Hook time.
• Off-hook time is the minimum time (msec) that the analogue line must stay in off-hook before the sys-
tem detects the off-hook state.
• On-hook time is the minimum time (msec) that the analogue line must stay in on-hook before the sys-
tem detects the on-hook state.
• Flash-hook. The flash-hool period may vary between countries, and the iMG flash-hook time parameter
allows the iMG user to allow for this. Note that flash-hook time can not be greater that on-hook time.