參數資料
型號： MT8843
廠商： Mitel Networks Corporation
英文描述： Calling Number Identification Circuit(主叫識別電路（提供各種主叫線信息傳遞設備的接口）)
中文描述： 主叫號碼識別電路（主叫識別電路（提供各種主叫線信息傳遞設備的接口））
文件頁數： 6/26頁
文件大?。?/td> 178K
代理商： MT8843
MT8843
5-36
When the dual tone alert signal is detected by the
CNIC2, ESt goes high. When the alerting signal
ceases to be detected, ESt goes low.
Dual Tone Detection Guard Time
The ESt pin signals raw detection of CAS/Alerting
Tones. Since both Bellcore and BT applications
require a minimum duration for valid signals, ESt
detection must be guard time qualified. The StD pin
provides guard time qualified CAS/Alerting Tone
detection. When the MT8843 is used in a caller
identity system StD indicates correct CAS/Alerting
Tone detection.
Figure 4 shows the relationship between the St/GT,
ESt and StD pins. It also shows the operation of a
guard time circuit.
The total recognition time is t
REC
= t
GP
+ t
DP
, where
t
GP
is the tone present guard time and t
DP
is the tone
present detect time (refer to timing between ESt, St/
GT and StD in Figures 16 and 19).
The total tone absent time is t
ABS
= t
GA
+ t
DA
, where
t
GA
is the tone absent guard time and t
DA
is the tone
absent detect time (refer to timing between ESt, St/
GT and StD in Figures 16 and 19).
Bellcore states that it is desirable to be able to turn
off CAS detection for an off-hook capable CPE. The
disable
switch
allows
disconnects a service that relies on CAS detection
(e.g., CIDCW) but retains the CPE, to turn off the
detector and not be bothered by false detection.
the
subscriber
who
When SW1 in Figure 4 is in the B position the guard
time circuit is disabled. The detector will still process
CAS/Alerting tones but the MT8843 will not signal
their presence by ensuring StD is low.
BT specifies that the idle state tone alert signal
recognition time should not be less than 20ms when
both tones are used for detection. That is, both tones
must be detected together for at least 20ms before
the signal can be declared valid. This requirement
can be met by setting the t
GP
(refer to Figure 5) to at
least 20ms.
BT also specifies that the TE is required to apply a
D.C. wetting pulse and an AC load 15-25ms after the
end of the alerting signal. If t
ABS
=t
DA
+t
GA
is 15 to
25ms, the D.C. current wetting pulse and the A.C.
load can both be applied at the falling edge of StD.
The maximum
t
DA
is 8ms so t
GA
should be 15-17ms.
Therefore, t
GP
must be greater than t
GA
. Figure 5(a)
shows a possible implementation. The values in
Figures 9 and 10 (R1=R2=422K, C=0.1
μ
F) will meet
the BT timing requirements.
Figure 4 - Guard Time Circuit Operation
Figure 5 - Guard Time Circuits with
Unequal Times
Input Configuration
The MT8843 provides an input arrangement
comprised of an operational amplifier and a bias
source (V
Ref
); which is used to bias the opamp inputs
at V
DD
/2
. The feedback resistor at the opamp output
(GS) can be used to adjust the gain. In a single-
ended configuration, the opamp is connected as
shown in Figure 6. For a differential input
configuration, Figure 7 shows the necessary
connections.
+
-
V
ESt
St/GT
V
DD
StD
= V
SS
Tones detected
From
detector
C
R
Q1
Q2
MT8843
Comparator
P
N
V
SS
SW1
B
A
(b) t
GP
< t
GA
t
GP
= R
P
C ln [V
DD
-V
D
(R
P
/R2))/(V
DD
-V
TGt
-V
D
(R
P
/R2))]
t
GA
= R1C ln (V
DD
/V
TGt
)
R
P
= R1R2/(R1+R2)
(a) t
GP
> t
GA
t
GP
= R1C ln [V
DD
/(V
DD
-V
TGt
)]
t
GA
= R
P
C ln [(V
DD
-V
D
(R
P
/R2))/(V
TGt
-V
D
(R
P
/R2))]
R
P
= R1R2/(R1+R2)
MT8843
V
DD
St/GT
ESt
R1
R2
C
V
D
=diode forward voltage
V
DD
St/GT
ESt
R1
R2
C
V
D
=diode forward voltage
MT8843
相關PDF資料
PDF描述
MT8888C Integrated DTMF Transceiver with Intel Micro Interface(雙音多頻信號（DTMF）收發(fā)器（帶Intel微接口）)
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MT8889CN-1 Integrated DTMFTransceiver with Adaptive Micro Interface
MT8889CS-1 Integrated DTMFTransceiver with Adaptive Micro Interface
MT8889C Integrated DTMFTransceiver with Adaptive Micro Interface
相關代理商/技術參數
參數描述
MT8843AE 制造商:Mitel Networks Corporation 功能描述:TELEPHONE CALLING NO IDENT CKT, PDIP24
MT8843AS 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:CMOS Calling Number Identification Circuit 2 Preliminary Information
MT8860 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:DTMF DECODER
MT8860XC 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:DTMF DECODER
MT8860XE 制造商:Hitachi 功能描述:DTMF RECEIVER, 18 Pin, Plastic, DIP 制造商:Microsemi Corporation 功能描述:DTMF RECEIVER, 18 Pin, Plastic, DIP 制造商:Mitel Networks Corporation 功能描述:DTMF RECEIVER, 18 Pin, Plastic, DIP
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