Question about EventDesc and EventBufferDesc(LockStep)

Hi all,
   I see both EventDesc and EventBufferDesc locate in one megaco message
with Buffer=LockStep.and I don't know how to understand it.

  package: 
   //it is sent to MG after one user offhook.
   //it intends to implement the strategy that MGC can collect dial
string in 2 parts. For example,301-0001.

    MEGACO/1 [10.177.128.76]:2944
Transaction = 25351 {
	Context = 0 {
		Modify = C0/1 {
			Media {
				TerminationState { Buffer=LockStep },
				Stream = 1 {
					LocalControl { Mode=ReceiveOnly
}
				}
			},
			Events = 34 {
				al/on, al/fl, ctyp/dtone, dd/ce {
DigitMap = dialplan0 }
			},
			EventBuffer { dd/ce },
			Signals {cg/dt },
			DigitMap=dialplan0 { T:8,S:0,L:8, ( [0-9EF]xx |
[0-9EF]x[EF] | [0-9EF][EF] ) }
		}
	}
}

  from rfc3525, 7.1.9 Events descriptor
        Case 1

      If EventBufferControl equals LockStep and the MG receives a new
      EventsDescriptor, it will check the FIFO EventBuffer and take the
      following actions:

     1) If the EventBuffer is empty, the MG waits for detection of
events
         based on the new EventsDescriptor.

It seems that we should detect event according to EventsDesc because
EventBuffer is NULL. but when the eventBuffer will be used to buffer
event?

for the megaco message,which explanation is right,or it has other
meaning?
1)only after first digit string detected and notified to MGC,EventBuffer
is used to buffer digit event and then wait another new EventDesc.
2)It just buffers digit according to  EventBufferDesc, and wait another
new EventDesc to notify event to MGC.

Thanks.

Best Regards.
Zhu Yi.

----------------------------------------------------------
Zhu Yi
FCG-ACD, Alcatel Shanghai Bell.
Tel:021-50554520-5778
Location: 10FC2, YinDong Building,No.58, Xinjinqiao Road
----------------------------------------------------------

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