Calling Line Identifier
MX602 - PRELIMINARY INFORMATION
15
if near end voice is muted. The choice of a specific strategy involves several tradeoffs which must be considered by the
end product designer.
As previously described, the MX602 dual tone detector and FSK energy level detector functions provide the tools to
implement a range of strategies. It is important to note that CIDCW transaction detection performance is influenced by
factors which are external to the MX602 and under the control of its surrounding circuit. Such factors may include:
(1) Input signal levels provided to the MX602, (2) The functional ‘cost’ associated with missed and false CIDCW
transaction detections, (3) Pulse width measurement accuracy, and (4) Noise or other disturbances introduced by muting
or other external circuits. The remainder of this section provides examples to assist end product designers develop their
specific designs.
CIDCW Transaction Initiation Detection Algorithm
The following State Transition Diagram Figure 16 and following text provide a detailed description of the CIDCW detection
procedure as shown in Figure 15.
1
INITIAL
DET goes high
DET goes low
Reset timer
DET goes low
Reset timer
Start timer
2
6
WAIT_T1
WAIT_DET_LOW
DET goes low
when timer is < T3
Timer = T1
Initiate local speech muting
Unmute local speech.
Reset timer
Timer = 65ms
3
Unmute local speech
MEAS_DET_HIGH
DET goes high
when timer is < 50ms
DET goes low when T3 < timer < 65ms
Set MX602 to
Tone Alert Detect Mode.
Unmute local speech.
Reset timer
Set MX602 to FSK Receive Mode.
Reset timer
4
CONFIRM_QUIET
CIDCW transaction complete
Timer = 50ms
Set MX602 to
Tone Alert Detect Mode.
Unmute local speech.
Reset timer
5
COMPLETE_CIDCW
Legend Example
STATE 0
STATE 1
Note: See text for details of times T1 & T3
Transition stimulus
Actions during transition
Figure 16, CIDCW State Flow Diagram
© 1998 MX•COM Inc.
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