H3C Technologies H3C MSR 50 - Manual (Page 596)

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Call services
More and more VoIP-based services are demanded as voice application environments expand. On basis
of basic calls, new features are implemented to meet different application requirements of VoIP
subscribers.
Call waiting
When subscriber C calls subscriber A who is already engaged in a call with subscriber B, the call is not
be rejected if call waiting is enabled. Just like a normal call, subscriber C hears ringback tones, while
subscriber A hears call waiting tones that remind that a call is waiting on the line.
Subscriber A can answer the new call by pressing the flash hook or hanging up to end the call with
subscriber B. In the former case, subscriber B is held. In the latter case, subscriber A is immediately
alerted and can pick up the phone to answer the call originated by subscriber C (the waiting call).
Call hold
If subscriber A in a conversation with subscriber B presses the flash hook, the media session of subscriber
B is temporarily cut through and is held (in the silent state or listening to the waiting tones). The system
plays silent tones or dial tones to subscriber A, depending on the configuration. (The system first plays
dial tones and waits for the subscriber to dial. If the subscriber fails to dial within a period of time, the
system stops playing dial tones and the line stays on hold.). Subscriber A can resume the call with
subscriber B by pressing the flash hook again.
After pressing the flash hook, subscriber A hears dial tones and can initiate a new call. The setup flow
for the new call is completely the same as the one for ordinary calls.
Call forwarding
After receiving a session request, the called party cannot answer the call for some reason. In this case,
the called party notifies in a response the calling party of the forwarded-to number so that the calling
party can re-initiate a session request to the new destination. This is call forwarding.
The system supports four different types of call forwarding:
• Call forwarding unconditional—With this feature enabled on a voice subscriber line, incoming
calls are forwarded to the predetermined destination, no matter whether the voice subscriber line is
available.
• Call forwarding busy—With this feature enabled on a voice subscriber line, an incoming call is
forwarded to the predetermined destination when the voice subscriber line is busy.
• Call forwarding no reply—With this feature enabled on a voice subscriber line, an incoming call is
forwarded to the predetermined destination when the voice subscriber line is not answered within
a period of time, which is configured by specifying Max Duration of Playing Ringback Tones on the
FXS, FXS or E&M line configuration page and defaults to 60 seconds.
• Call forwarding unavailable—With this feature enabled on a voice subscriber line, an incoming
call is forwarded to the predetermined destination when the voice subscriber line is shut down.