Data Sheet
MT88E45B
CPE unmutes handset
CPE goes off-hook
CPE mutes handset & disables keypad
CPE sends
and enables keypad
TIP/RING
Note 5
Mark
Data
F
CAS
A
ACK
C
Note 1
E
G
B
D
PWDN
Note 8
Hybrid CASen
Note 8
Note 2
Note 3
Note 4
FSKen
Note 8
tPU
OSC2
EST
tDP
tDA
tGA
VTGt
tGP
ST/GT
tREC
tABS
STD
Note 9
tCP
tCA
Note 6
Note 7
CD
A = 75-85ms
B = 0-100ms
C = 55-65ms
D = 0-500ms
E = 58-75ms
DR
Note 9
DCLK
DATA
F = feature specific
G ≤ 50ms
Data
Figure 16 - Application Timing for Bellcore Off-hook Data Transmission, e.g., CIDCW
Notes:
1) In a CPE where AC power is not available, the designer may choose to switch over to line power when the CPE goes off-hook and
use battery power while on-hook. The CPE must also be CID (on-hook) capable because a CIDCW CPE includes CID functionality.
2) Non-FSK signals such as CAS, speech and DTMF tones are in the same frequency band as FSK. They will be demodulated and
give false data. Therefore the MT88E45B should be taken out of FSK mode when FSK is not expected.
3) The MT88E45B may be put into FSK mode as soon as the CPE has finished sending the acknowledgment signal ACK. TR-NWT-
000575 specifies that ACK = DTMF ‘D’ for non-ADSI CPE, ‘A’ for ADSI CPE.
4) The MT88E45B should be taken out of FSK mode when CD has become inactive, or after 5 framing errors have been detected, or
after 150ms of continuous mark signal or space signal has been received. The framing errors need not be consecutive.
5) In an unsuccessful attempt where the end office does not send the FSK signal, the CPE should unmute the handset and enable the
keypad after interval D has expired.
6) The total recognition time is tREC = tGP + tDP , where tGP is the tone present guard time and tDP is the tone present detect time. VTGt
is the comparator threshold (refer to Figure 5 for details).
7) The total tone absent time is tABS = tGA + tDA , where tGA is the tone absent guard time and tDA is the tone absent detect time. VTGt
is the comparator threshold (refer to Figure 5 for details).
8) PWDN, Hybrid CASen and FSKen are internal signals decoded from CB0/1/2.
9) This signal represents the mode of the DR/STD pin.
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