Calling Line Identifier
MX602 - PRELIMINARY INFORMATION
17
Adjunct Box Timing
When the CIDCW circuits are housed in an adjunct box so that muting is only possible by interrupting the 2-wire
connection to the telephone set, then it is recommended that:
T1 should be 15ms i.e. speech muting should only be initiated after the DET output has been high for 15ms.
T2, the time for speech muting to take effect, should be as short as possible and in any case not more than 5ms.
T3, the minimum length of a valid DET output high time, should be equal to T1 plus T2 plus 10ms, i.e. between 25 and
30ms.
Telephone Set Timing
When the CIDCW circuits are built into the telephone set so that locally generated speech can be muted quickly and
without injecting noise then it is recommended that:
T1 should be zero, i.e. muting should be initiated as soon as the MX602 DET output goes high.
T2, the time for local speech muting to take effect, should be as short as possible and in any case not more than 5ms.
T3, the minimum length of a valid DET output high time, should be 15ms.
Notes:
1. The T1, T2, and T3 time values are intended to provide guidance, however, different times may be required for
optimal operation in specific end product designs.
2. For optimum performance, the system transition times from tone detect to muting and tone detect de-response to FSK
mode should be minimized. Tests have been performed with sub-millisecond response times but longer times may be
used with some degradation in performance.
3. The 50ms monitoring period of the CONFIRM_QUIET state, when added to the 0.5 to 10ms de-response time of the
MX602 in Tone Alert Detect and a nominal 0 to 5ms delay in changing from TONE mode to FSK mode, results in a
valid CAS detection occurring at between 50 and 65ms after the end of the CAS. This leaves at least 35ms to mute
the local handset fully, test for off-hook extensions, and initiate the DTMF ACK tone within the time permitted by
CIDCW specifications.
4. During the CONFIRM_QUIET state, any high pulses on the DET output will last for at least 8ms (or until the mode is
changed). This makes it simple to monitor and detect any DET high output pulses when in this state.
5. In adjunct box applications, it is important to avoid injecting noise to the MX602 input signal when performing near end
voice muting because such noise could disrupt MX602 operation and reduce performance. Alternate approaches can
be used which would delay such voice muting until after the CAS tone. One example would first qualify dual tone
detector output pulses of 20ms to 65ms nominal duration as CAS tone indications and follow such pulses with near
end voice muting and silence confirmation to further enhance performance.
5.2.4 Block Diagrams of Adjunct Box and Telephone Set Interfaces
Central
Office
CPE (phone)
hook
switch
ring
tip
nc
Line
Hold
Ckt.
RD
RT
RXD
RXCLK
DET
Input
Interface
Components
(R, C, D)
Line
Protection
Network
µC
AMPOUT
MX602
IN-
mute control
IRQ
ZP
IN+
Caller Identity Display,
User Interface, etc.
Figure 17: Adjunct Box Interface
© 1998 MX•COM Inc.
www.mxcom.com Tele: 800 638-5577 336 744-5050 Fax: 336 744-5054
Doc. # 20480136.004
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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