Nortel Media Gateway 3200 User Manual page 92

Using these packages, the MG 3200 converts from the MFC-R2 protocol, which is a PSTN
protocol, to the H.248 protocol, thereby bridging the PSTN world with the IP world.
Note:
When H.248 and MFC-R2 protocols share control of a channel, their timings are
synchronized so that H.248 commands do not cause damage to the MFC-R2 protocol's
negotiation. For example, MFC-R2 protocol must work with the Echo Canceler in OFF state
or else Multiple Frequency (MF) is not received correctly. Thus, if H.248 protocol receives a
command to open a channel with the Echo Canceler ON and MFC-R2 protocol's
negotiation is not yet finished, the entire negotiation could be damaged. To avoid this
problem, the H.248 will not change the echo canceler state until the call was accepted by
the answering side.
The actual call should start only after the accept signal is finished. (See the call flow of call
start).
The application supports a special option called re-answer. In this option, the answering
side can put down the phone, and pick it up again. The phone close will result with the
'icas/cb' event, but if the phone is taken up again, the 'bcas/ans' event will be sent. The
timing of this action is defined by the MGC. It is the MGC responsibility to decide when the
call should be disconnected by sending the 'icas/cf' signal. (refer to the figures below for
the call flow of the call disconnect for the use of these signals and events).
User's Manual
Currently only E1-MFCR2 protocol is supported, there is no R1 support or
T1 support.
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MG 3200
Document # LTRT-72704