Preliminary Information
MH89760B
MH89760B
DIP
High Speed
Parallel
Telecom Bus
MT8920B
(Mode 2)
Switch
MT8976
OUTA
D -D
Tx
0
7
5
DSTi
TxA
TxB
STo0
STi0
EQU
Line
Driver
DSTo
A -A
0
STo1
CSTi0
CSTo
CSTi1
OUTB
RxT
MH89761
CS
R/W
OE
C4i
F0i
Rx
F0i
RxA
RxB
•
•
Line
C2i
•
Driver
MMS MS1 24/32
C1.5i
RxR
+5V
RxD
•
Signalling and
Link Control
BUS
MT8920B
(Mode 1)
E8Ko
E1.5i
D -D
STo0
STi0
0
7
A -A
0
5
STo1
Clock
Extractor
CS
DS
R/W
C4i
F0i
•
DTACK
IRQ
•
MT8941
IACK
12.352 MHz
Osc.
1.544 MHz
CVb
MMS
+5V
F0i
C2o
F0b
16.384 MHz
Osc.
•
C4b
C8Kb
Figure 12 - Using the MH89760B in a Parallel Bus Environment
the signalling and link control bus to the MH89760B
status and control channels. All signalling and link
functions may be controlled easily through the STPA
transmit RAM’s Tx0, Tx1, while status information is
read at receive RAM Rx0. In addition, interrupts can
be set up to notify the system in case of slips, loss of
sync, alarms, violations, etc.
Figure 13 shows a block diagram of a channel bank
that has been divided into four sections, the analog
line interface, signalling interface, switch matrix, and
T1 interface. The subscriber line interface circuit
(SLIC) provides interface to the telephone line, i.e.,
provides loop current and ringing voltage, and
converts the analog voice signal into µ-Law PCM.
The SLIC also detects the off-hook condition for
conventional POTS (Plain Old Telephone Set)
signalling.
3. PCM/Voice Channel Bank
The D3/D4 channel bank is one of the most widely
used pieces of equipment in the North American
network today. The D3/D4 channel converts 24
analog telephone lines into the 24 channels of a T1
serial stream. The channel bank is the interface point
between a digital switching or transmission system
and the analog telephone loop. The industry is
moving towards end-to-end digital connections
(ISDN), but the analog channel bank will still be in
use for many years to come.
Once the voice is encoded into digital format the
switch matrix transfers the 24 consecutive channels
that are received from the SLICs to the 24 valid
channels used by the MH89760B. The MH89760B
formats and transmits this information on the T1 line.
Signalling information from the telephone sets can
be routed straight through to the output T1 channel,
or it can be routed to the DTMF receiver pool. This is
4-73
MITEL [ MITEL NETWORKS CORPORATION ]
