MT88E43B
Item
Low tone
frequency
High tone
frequency
Received
signal level
BT
2130Hz
±1.1%
2750Hz
±
1.1%
-2dBV to -40dBV
per tone on-hook
1
(0.22dBm
2
to
-37.78dBm)
-46dBV
(-43.78dBm)
up to 7dB
Bellcore
2130Hz
±0.5%
2750Hz
±
0.5%
-14dBm
b
to
- 32dBm per tone
off-hook
-45dBm
up to 6dB
Data Sheet
Signal reject
level
Signal level
differential
(twist)
Unwanted
signals
Duration
Speech
present
<= -20dB
(300-3400Hz)
88ms to 110ms
4
No
<= -7dBm ASL
3
near end speech
75ms to 85ms
Yes
Table 1 - Dual Tone Alert Signal Characteristics
1. In the future BT may specify the off-hook signal level as
-15 dBm to -34 dBm per tone for BT CIDCW.
2. The signal power is expressed in dBm referenced to 600 ohm
at the CPE A/B (tip/ring) interface.
3. ASL = active speech level expressed in dBm referenced to
600 ohm at the CPE tip/ring interface. The level is measured
according to method B of Recommendation P.56 "Objective
Measurement of Active Speech Level" published in the CCITT
Blue Book, volume V "Telephone Transmission Quality" 1989.
EPL (Equivalent Peak Level) = ASL+11.7 dB
4. SIN227 suggests that the recognition time should be not less
than 20 ms if both tones are detected.
Dual Tone Detection Guard Time
When the dual tone alert signal is detected by the MT88E43, ESt goes high. When the alerting signal ceases to be
detected, ESt goes low.
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 MT88E43 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 17 and 20).
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 17 and 20).
6
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
